Geol.Lib. 

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THE  LIBRARY 

OF 

THE  UNIVERSITY 

OF  CALIFORNIA 

LOS  ANGELES 


U.  S.  DEPARTMENT  OF  AGRICULTURE, 

BUREAU  OF  SOILS— MILTON  WHITNEY,  Chief. 


Lh! 


IN  COOPERATION  WITH  THE  UNIVERSITY  OF  CALIFORNIA  AGRICULTURAL 

EXPERIMENT  STATION,  THOMAS  F.  HUNT,  DIRECTOR;  CHARLES  F. 

SHAW,  IN  CHARGE  SOIL  SURVEY. 


50IL  SURVEY  OF  THE  EL  CENTRO  AREA, 
CALIFORNIA. 


T.  STRAHORN,  In  Charge,  E.  B.  WATSON,  A.  E.  KOCHER, 
and  E.  C.  ECKMANN,  of  the  U.  S.  Department  of  Agri- 
culture, and  J.  B.  HAMMON,  of  the 
University  of  California. 


MACY  H    LAPHAM,  Inspector,  Western  Division. 


[Advance  Sheets— Field  Operations  of  the  Bureau  of  Soils,  1918.] 


WASHINGTON: 

GOVERNMENT  PRINTING  OFFICE. 

1922 


UNIVERSITY  OF  CALIFORNIA 
GEOLOGY-GEOPHYSICS  LIBRARY 

405  HTLGARD  ATE. 
LOS  ANGELES,  CALIF.  90024 


BUREAU  OF  SOILS. 

Milton  Whitney.  Chief  of  Bureau. 
Albert  G.  Rice.  Chief  Clerk. 

.  SOIL   SURVEY. 

Curtis  F.  Marbut.  In  Charge. 
G.  W.  Baumann,  Executive  Assistant. 

COMMITTEE  ON   THE  CORRELATION   AM)   CLASSIFICATION*   OF   SOILS. 

Curtis  F.  Marbut.  Chairman. 
High  H.  Bennett.  Inspector,  Southern  Division. 
W.  Edward  Hearn,  Inspector,  Southern  Division. 
Thomas   D.   Rice,    Inspector.   Northern   Division. 
W.  E.  M<  Lendon,  Inspector,  Northern  Division. 
Macy  H.  Lapham,  Inspector,  Western  Division. 

Louise  L.  Martin,  Secretary. 


U.  S.  DEPARTMENT  OF  AGRICULTURE, 

BUREAU  OF  SOILS— MILTON  WHITNEY,  Chief. 

IN  COOPERATION  WITH  THE   UNIVERSITY  OF  CALIFORNIA  AGRICULTURAL 

EXPERIMENT  STATION,  THOMAS  F.  HUNT,  DIRECTOR;  CHARLES  F. 

SHAW,  IN  CHARGE  SOIL  SURVEY. 


SOIL  SURVEY  OF  THE  EL  CENTRO  AREA, 
CALIFORNIA. 


BY 


A.  T.  STRAHORN,  In  Charge,  E.  B.  WATSON,  A.  E.  KOCHER, 
and  E.  C.  ECKMANN,  of  the  U.  S.  Department  of  Agri- 
culture, and  J.  B.  HAMMON,  of  the 
University  of  California. 


MACY  H   LAPHAM,  Inspector,  Western  Division. 


[Advance  Sheets— Field  Operations  of  the  Bureau  of  Soils,  1918.] 


WASHINGTON: 

GOVERNMENT  PRINTING   OFFICE. 

1922 


LETTER  OF  TRANSMITTAL. 


U.  S.  Department  of  Agriculture, 

Bureau  of  Soils, 
Washington,  D.  C,  June  25,  1921. 
Sir  :  In  the  extension  of  the  soil  survey  in  the  State  of  California 
during  the  field  season  of  1918  a  survey  was  undertaken  in  the  El 
Centro  area.    This  work  was  done  in  cooperation  with  the  University 
of  California  Agricultural  Experiment  Station. 

I  have  the  honor  to  transmit  herewith  the  manuscript  report  and 
map  covering  this  work  and  to  request  their  publication  as  advance 
sheets  of  Field  Operations  of  the  Bureau  of  Soils  for  1918,  as  au- 
thorized by  law. 

Respectfully, 

Milton  Whitney, 

Chief  of  Bureau. 
Hon.  H.  C.  Wallace, 

Secretary  of  Agriculture. 


\ 


o 

^3 


library 


5  ' 


CONTENTS. 

Page. 
Soil  Survey  of  the  El  Centeo  Area,  California.    By  A.  T.  Strahorn, 
In  Charge,  E.  B.  Watson,  A.  E.  Kocher,  and  E.  C.  Eckmann,  of  the 
U.  S.  Department  of  Agriculture,  and  J.  B.  Hammon,  of  the  Uni- 
versity of  California 5 

Description  of  the  area 5 

Climate 10 

Agriculture 12 

Soils. 18 

Imperial  silty  clay  loam 26 

Imperial  silty  clay . 27 

Imperial  clay 29 

Holtville  very  fine  sandy  loam 31 

Holtville  silty  clay  loam 32 

Holtville  silty  clay 33 

Holtville  clay 34 

Tijeras  gravelly  fine  sandy  loam 35 

Superstition  gravelly  coarse  sand 36 

Superstition  coarse  sand 36 

Superstition  gravelly  sand 37 

Superstition  fine  sand 38 

Meloland  gravelly  sand 39 

Meloland  fine  sand 40 

Meloland  fine  sandy  loam 41 

Rositas  gravelly  fine  sand 42 

Rositas  sand 42 

Rositas  fine  sand : 43 

Rositas  very  fine  sand 44 

Rositas  very  fine  sandy  loam 45 

Carrizo  sand 46 

Riverwash 47 

Rough  broken  land 47 

Dunesand 47 

Irrigation 48 

Alkali 51 

\_j     Summary 57 


573934  3 


ILLUSTRATIONS. 


PLATER. 

Page. 
Plate  I.  Fig.  1. — View  near  Holtville  showing  gorge  of  Alamo  River. 

Big.  2. — Cattle  grazing  on  alfalfa  in  winter  season 16 

II.  Fig.  1. — Cotton  stored  in  yard  at  Imperial.  Fig.  2. — Topog- 
raphy and  characteristic  surface  gravel  (desert  pavement)  on 
Superstition   gravelly   sand 16 

III.  Fig.   1. — Imperial   silty   clay   prepared   for  planting  to  musk- 

melons.     Fig.  2. — Alfalfa  grown  as  a  soiling  crop  on  Melo- 

land  fine  sandy  loam 4S 

IV.  Fig.  1. — Rositas  very  fine  sand  near  Holtville.     Fig.  2. — View 

looking  down  roadway  showing  wall  of  silt  deposits  removed 
from  irrigation  canal  on  left 4S 

FIGURE. 

Fig.  1.  Sketch  may  showing  location  of  the  El  Centro  area,  California 5 

MAPS. 

Soil  map,  El  Centro  sheet,  California. 
Alkali  map,  El  Centro  sheet,  California. 
4 


SOIL  SURVEY  OF  THE  EL  CENTRO  AREA, 
CALIFORNIA. 

By  A.  T.  STRAHORN,  In  Charge,  E.  B.  WATSON,  A.  E.  KOCHER,  and  E.  C. 
ECKMANN,  of  the  U.  S.  Department  of  Agriculture,  and  J.  B.  HAMMON,  of 
the  University  of  California. — Area  Inspected  by   MACY   H.   LAPHAM. 

DESCRIPTION  OF  THE  AREA. 

The  extreme  southern  portion  of  California,  the  northern  limits  of 
which  are  quite  definitely  marked  by  ranges  of  hills  and  mountains 
extending  from  the  Pacific  Ocean,  just  north  of  Santa  Monica,  east- 
ward to  the  Colorado  River,  is  divided  by  the  Peninsula  Range  of 
mountains  into  what  are  known  as  the  coast  and  desert  regions'. 
This  range  begins  at  Mount  San  Jacinto  and  extends  southerly  into 
the  Mexican  territory  of  Lower  California.  Its  eastern  front  is  a 
steep  rugged  escarpment ;  west  of  its  crest  the  mountainous  region  is 
a  complicated  system  of  small  mountain 
valleys  and  ridges,  the  drainage  of  which 
is  into  the  Pacific  Ocean. 

The  desert  region,  which  is  known  as  the 
Colorado  Desert,  includes  an  area  between 
the  Peninsula  Range  on  the  west;  the 
Cottonwood,  Chocolate,  and  Chucawalla 
Mountains  and  the  Colorado  River  on  the 
north  and  east;  and  a  line  in  Lower  Cali- 
fornia on  the  south.  The  area  of  this 
desert  is  about  8,000  square  miles,  the 
larger  part  lying  within  the  United  States. 
Approximately  2,200  square  miles  of  it 
lie  below  sea  level  and  was  formerly 
known   as   Salton   Sink,1  consisting  of   a 

depression  surrounded  by  a  nearly  continuous  beach  line,  now  slightly 
above  present  sea  level,  which  marks  the  extent  of  a  former  extensive 
body  of  water  that  occupied  this  part  of  the  desert. 

The  old  beach  line  plainly  divides  the  desert  into  two  physio- 
graphic divisions,  the  lower  including  the  Imperial  Valley  and  Salton 

1  The  term  "  Salton  Sink  "  was  originally  applied  to  all  of  the  depression  included 
within  the  old  beach  line,  but  since  the  occupation  and  devolpment  of  the  desert  by  man, 
the  term  usually  has  been  applied  to  the  lowest  part,  at  present  occupied  by  a  body  of 
water  known  as  the  Salton  Sea.  The  term  "  Imperial  Valley  "  refers  to  the  adjacent 
areas,  now  largely  under  irrigation. 

5 


A£r~ 

ES 

Fig.  1. — Sketch  map  showing 
location  of  the  Bl  Centro 
area,   California. 


6  I'll  1.1'    OPERATIONS    OF   THE   BUREAU   OF   SOILS,   1018. 

sink  and  the  upper,  all  of  the  extensive  and  irregular  desert  areas 
lying  between  the  old  beach  line  and  the  outer  limits  of  the  Colorado 
Desert  region.  The  first  is  a  uniform  plain,  sloping  gently  to  the 
north,  the  surface  of  which  is  broken  only  by  the  channels  of  New 
and  Alamo  Rivers,  and  by  occasional  bodies  of  Dunesand.  Its  eleva- 
tion ranges  from  about  35  feet  above  sea  level,  along  the  old  beach 
line,  to  287  feet  below  sea  level  at  the  lowest  point.  The  areas  above 
the  beach  line  consist,  for  the  larger  part,  of  uniform  to  moderately 
rolling  plains  rising  gradually  to  the  several  boundaries.  Shallow 
intermittent  stream  ways  have  given  rise  to  local  irregularities,  and 
occasional  partly  buried  mountain  masses  and  extensive  sand  dunes 
form  the  only  conspicuous  elevations  above  the  general  level  of  the 
surface.  This  part  of  the  desert  has  its  lowest  elevation  along  the 
old  beach  line  about  35  feet  above  sea  level  and  its  highest  about  500 
feet  above  sea  level,  at  the  bases  of  the  bordering  mountains,  and  in 
the  isolated  prominences  on  the  floor  of  the  desert,  which  range  from 
500  to  over  2,000  feet  above  sea  level. 

The  El  Centro  area  is  located  in  Imperial  County  in  the  extreme 
southern  part  of  the  Colorado  Desert,  the  southern  boundary  of  the 
area  being  the  international  boundary  line  between  the  United  States 
and  Mexico.  The  northern,  eastern,  and  western  boundaries  of  the 
area  are  formed  by  certain  section  and  township  lines  of  the  recent 
resurvey  of  this  region  by  the  United  States  Land  Office.  The  east- 
ern boundary  line  of  the  area  is  about  35  miles  west  of  the  California- 
Arizona  State  line.  The  area  surveyed  has  an  extent  of  540  square 
miles,  or  322,560  acres. 

Prior  to  1905  and  1906  the  only  evident  irregularities  in  topog- 
raphy of  the  surface  were  the  shallow  depressions  serving  as  the 
channels  of  Xew  and  Alamo  Rivers,  a  low  escarpment  around  what 
was  known  as  Mesquite  Lake,  and  a  number  of  large  bodies  of  Dune- 
sand.  Extensive  areas  of  land  were  literally  as  smooth  as  a  floor, 
but  over  much  of  the  area  the  surface  was  dotted  with  small  mounds 
of  wind-blown  material  lodged  on  the  windward  side  of  clumps  of 
desert  vegetation. 

During  a  period  of  several  months  in  1905  and  1906  the  Colorado 
River,  instead  of  following  its  usual  course  to  the  Gulf  of  California 
in  Mexico,  turned  its  flood  into  this  basin  and  occupied  the  channels 
of  the  Xew  and  Alamo  Rivers.  During  the  early  periods  of  the 
flood  from  the  Colorado  River  these  old  channels  were  entirely 
inadequate,  and  the  waters  spread  out  over  extensive  adjacent  areas. 
The  slope  of  the  valley  was  sufficient  to  give  the  water  considerable 
velocity,  and  the  erosion  of  the  former  channels  of  the  streams, 
beginning  at  a  point  near  the  Sink,  progressed  rapidly  southward 
to  some  distance  south  of  the  international  boundary  line.     This 


SOIL   SURVEY   OF   THE   EL   CENTEO   AREA,    CALIFORNIA.  7 

erosion  was  most  severe  along-  the  channel  of  New  River,  the  results 
being  a  sinuous  gorge  some  30  miles  long  and  50  to  100  feet  or  more 
deep  with  numerous  tributary  channels,  some  of  which  were  but 
little  smaller  than  the  main  gorge.  The  banks  of  these  channels  for 
the  greater  part  of  their  length  are  vertical  from  the  top  nearly  to 
the  bottom.     (PL  I,  Fig.  1.) 

The  immediate  flood  plain  of  New  River  is  but  little  above  the 
normal  water  surface  of  that  stream  and  is  subject  to  recurring  over- 
flows when  unusually  large  volumes  of  waste  irrigation  water  are 
turned  into  the  stream.  The  area  of  this  flood  plain  forms  but  a 
small  part  of  the  bottom  of  the  gorge,  the  larger  part  being  eroded 
and  lying  several  feet  above  the  flood  plain. 

The  former  channel  of  the  Alamo  River  has  suffered  less  from  the 
effects  of  the  flood  than  that  of  New  River.  In  places  it  is  hardly 
50  feet  wide  and  less  than  20  feet  deep ;  in  other  places  it  may  be 
more  than  half  a  mile  in  width  and  have  a  depth  of  100  feet  or 
more.2  The  immediate  channel  of  this  stream  has  developed  no 
flood  plain,  but  is  depressed  several  feet  below  the  adjacent  low- 
lands. These  latter  may  be  either  rolling  eroded  lands  or  occur  as 
fairly  uniform  or  rolling  terraces,  of  which  as  many  as  three  exist 
in  several  localities. 

Mesquite  Lake,  which  lies  several  miles  east  of  the  town  of  Imperial, 
is  a  shallow  flat-bottomed  depression  bordered  by  a  low  eroded  escarp- 
ment. Prior  to  the  time  of  the  flood,  this  occasionally  carried  over- 
flow waters  from  the  Alamo  River.  At  the  time  of  the  flood,  a  new 
connection  was  made  with  the  Alamo  at  a  lower  point,  so  as  to  assist 
in  the  removal  of  the  flood  waters,  and  the  former  inlet  was  closed. 

On  the  eastern  side  of  the  valley,  the  sea-level  contour  enters  the 
area  near  the  northeastern  corner,  passes  southward  about  4  miles 
east  of  Holtville,  thence  a  few  miles  in  a  southerly  direction  and, 
swinging  sharply  northward,  returns  to  a  point  about  a  mile  south 
of  the  town  of  Holtville.  Its  course  is  then  southwesterly,  passing 
across  the  international  boundary  line  at  the  junction  of  the  latter 
and  the  channel  of  New  River.  On  the  western  side  of  the  valley,  this 
contour  parallels  the  old  beach  line  very  closely,  lying  about  one-half 
mile  east  of  it.  Most  of  the  towns  within  the  area  lie  below  sea  level, 
El  Centro  having  an  elevation  of  about  50  feet;  Imperial,  about  67 
feet;  Heber,  17  feet;  Holtville,  10  feet;  and  Seeley,  25  feet  below 
sea  level.    Calexico  is  about  5  feet  above  sea  level. 

2  "  la  the  period,  about  nine  months,  when  the  flood  waters  of  the  Colorado  River  were 
flowing  down  to  Salton  Sink,  the  waters  carried  away  a  yardage  of  earth  almost  four 
times  that  excavated  from  the  Panama  Canal.  The  combined  length  of  the  channels  cut 
out  was  almost  43  miles,  the  siverage  width  being  1,000  feet,  and  the  depth  50  feet.  To 
this  total  of  from  400,000,000  to  500,000,000  yards  of  earth  must  be  added  almost 
10  per  cent  more  for  side  canyons,  surface  land  erosion,  etc."  (Transactions,  American 
Society  of  Civil  Engineers,  Professional  Paper  No.  1270,  p.  1324,  II.  T.  Corey.) 


S  FIELD  OPERATIONS   OF   THE  BUREAU    OF   SOILS,   1018. 

On  the  western  side  of  the  valley,  the  old  beach  Line  has  an  eleva- 
tion of  about  35  feet  above  sea  level.  West  of  that  line,  there  is  a 
gradual  increase  in  elevation,  the  southwestern  corner  of  the  area 
lying  about  L50  feet  above  sea  level.  On  the  eastern  side  of  the  valley 
the  elevation  of  the  beach  line  is  about  50  feet  above  sea  level  and 
the  limited  area  of  desert  land  lying  between  that  line  and  the  eastern 
boundary  of  the  area  is  slightly  both  above  and  below  that  elevation. 

The  higher  desert  parts  of  the  area  on  the  western  side  of  the  valley 
have  a  marked  fall  toward  the  axis  of  the  valley,  and  the  drainage  of 
this  region  is  eifected  by  numerous  characteristic  desert  drainage 
ways.  These  are  wide,  shallow,  sandy  bottomed  water  courses,  often 
having  poorly  defined  banks.  These  channels  are  dry  year  after 
year,  and  carry  water  for  a  brief  interval  only  after  long  and  heavy 
storms  in  the  higher  mountains  or  adjacent  desert  regions.  Xone  of 
the  water  reaches  any  large  streams,  all  of  it  being  absorbed  by  the 
sands  within  a  short  distance  below  the  old  beach  line.  On  the  eastern 
desert  the  surface  relief  is  too  low  and  flat  to  form  any  system  of 
surface  drainage. 

Within  the  present  irrigated  area  there  are  few  surface  drainage 
channels.  The  slope  of  the  land  to  the  north  would  be  sufficient  to 
develop  drainage  courses  in  a  region  of  heavier  precipitation,  but 
the  small  and  very  infrequent  rainfall  of  this  region  is  not  sufficient 
to  form  even  local  arroyos  or  gullies.  The  channels  of  New  and 
Alamo  Rivers  afford  a  means  of  removing  waste  irrigation  waters 
from  canals  and  from  adjacent  lands,  and  wasteways  have  been 
constructed  to  those  streams  for  the  purpose  of  regulating  the  flow 
of  water  in  the  canals. 

Spanish  explorers  and  padres  from  the  early  missions  in  what 
is  now  Arizona  and  New  Mexico  and  in  the  northern  part  of  Mexico 
carried  on  extensive  explorations  throughout  the  Southwest  early 
in  the  sixteenth  century,  and  two  parties  explored  the  lower  Colo- 
rado River  as  early  as  1540.  What  is  now  known  as  the  Salton 
Sink  and  the  Imperial  Valley  were  probably  seen  during  that  year, 
and  following  the  founding  of  the  several  missions  in  southern  Cali- 
fornia early  in  the  eighteenth  century  it  is  probable  that  there  was 
more  or  less  travel  between  them  and  the  missions  east  of  the  Colo- 
rado River. 

A  number  of  explorations  were  made  by  Americans  at  various 
times  after  1825,  the  most  notable  being  that  of  the  Williamson  party 
in  1853.  That  party  had  for  its  object  the  discovery  of  a  pass 
across  the  western  mountains  for  a  railroad  route  to  the  Pacific 
coast,  and  during  the  exploration  they  crossed  the  northern  portion 
of  this  desert.  In  1851  Butterfield  established  a  stage  route  across 
the  desert  from  Yuma  to  the  coast,  the  route  crossing  the  southern 
portion  of  the  El  Centro  area.     This  route  was  in  continual  opera- 


SOIL  SURVEY   OF   THE   EL   CENTRO   AREA,    CALIFORNIA.  9 

tion  until  in  1879,  when  the  Southern  Pacific  Railroad  was  con- 
structed from  Yuma  to  Los  Angeles. 

Prior  to  the  construction  of  the  present  irrigation  system  the  popu- 
lation of  the  desert  was  confined  to  the  few  people  at  each  of  the 
railroad  stations  along  the  line  of  the  railroad  and  the  few  Indians 
on  the  Yuma  Indian  Reservation  along  the  Colorado  River.  Facil- 
ities for  irrigation  soon  attracted  large  numbers  of  farmers  to  the 
area.  The  desert  may  be  said  to  have  had  no  permanent  population 
in  1900;  in  1910,  according  to  the  Federal  census,  Imperial  County 
had  a  population  of  13,591,  the  larger  part  of  whom  resided  in  the 
Imperial  Valley.  In  1910  the  population  of  the  El  Centro  area  was 
about  8,800  and  in  1917  it  was  estimated  (school  census)  to  be  about 
28,000.  The  population  of  Imperial  County  in  1920  had  reached 
43,453.  Before  the  development  of  the  present  irrigation  system 
this  district  was  included  in  San  Diego  County,  but  in  1907  the 
eastern  part  of  that  county  was  separated  to  form  Imperial  County, 
with  El  Centro  as  the  county  seat. 

El  Centro,  established  in  1906,  had  a  population  of  1,610  in  1910. 
According  to  the  1920  census  the  population  is  5,464.  This  place  lies 
about  30  miles  south  of  the  main  line  of  the  Southern  Pacific  Rail- 
road, on  the  Imperial  Valley  branch  of  that  line,  and  is  the  present 
eastern  terminus  of  the  San  Diego  &  Arizona  Railroad,  a  line  re- 
cently completed  between  El  Centro  and  San  Diego.  A  local  rail- 
road, the  Holton  Interurban,  extends  eastward  from  El  Centro  for 
about  11  miles  to  the  town  of  Holtville. 

Calexico,  9  miles  southeast  of  El  Centro,  is  located  on  the  Mexi- 
can border,  just  within  the  United  States.  Its  population,  which 
in  1910  numbered  797,  in  1920  had  increased  to  6,223.  It  is  at  the 
southern  terminus  of  the  Imperial  Valley  branch  of  the  Southern 
Pacific,  and  a  continuation  of  that  line,  known  as  the  Inter-California 
Railway,  extends  southeasterly  through  Mexican  territory,  and  meets 
the  main  line  of  the  Southern  Pacific  at  Yuma,  Ariz. 

Imperial,  which  was  the  first  town  to  be  established  in  the  valley, 
is  4  miles  north  of  El  Centro.  Its  population  in  1910  was  1,257, 
and  in  1920,  1,825.  The  population  of  Holtville,  situated  11  miles 
east  of  El  Centro,  was  727  in  1910  and  1,347  in  1920.  Seeley,  9  miles 
west  of  El  Centro,  Dixieland,  on  the  edge  of  the  desert,  just  west 
of  the  Main  West  Side  Canal,  and  about  13  miles  west  of  El  Centro, 
and  Heber,  6  miles  southeast  of  El  Centro,  are  smaller  towns  in 
the  area. 

The  main  line  of  the  Southern  Pacific  Railroad,  between  Los  An- 
geles and  New  Orleans,  passes  across  the  northern  part  of  the  desert, 
about  25  miles  north  of  the  northern  boundary  of  the  El  Centro 
area,  and  a  branch  of  that  line,  known  as  the  Imperial  Valley  branch, 
passes  southwesterly  through  the  central  portion  of  this  area. 
58142°— 22 2 


10  FIELD  OPF.rtATioxs  of  Tin-:   r.rur.vr   OF  SOILS,  1!>18. 

One  link  of  the  State  highway  system,  a  concrete  highway  20  feet 
in  width,  extends  westward  from  El  Centro  beyond  the  limits  of 
the  area.  Except  in  the  more  thinly  settled  portions  of  the  area,  or 
where  there  are  considerable  areas  of  wind-blown  sand,  good  dirt 
roads  occur  on  nearly  every  section  line,  and  in  some  localities  are 
only  a  half  mile  apart.  All  the  main  roads  are  about  twice  as  wide 
as  the  usual  country  road,  and  are  divided  into  two  parts  by  a  low 
ridge,  or  levee,  extending  down  the  center.  As  the  rains  in  this 
region  are  not  sufficient  to  keep  down  the  dust  and  maintain  the 
surface  of  the  road  in  a  favorable  condition  for  travel,  the  practice 
is  to  flood  the  road,  at  intervals,  on  one  side  of  the  levee  and  restrict 
travel  to  the  other  side.  "When  the  flooded  side  has  become  dry  and 
is  in  the  proper  condition  traffic  is  diverted  to  it  and  the  opposite 
side  is  then  covered  with  water.  In  addition  to  the  regular  roads 
there  are  narrow  roads  along  the  tops  or  at  the  base  of  the  canal 
banks,  which  are  largely  used  by  ditch  riders  in  the  performance  of 
their  duties. 

The  outside  markets  for  the  products  of  the  area  cover  the  entire 
country.  Lettuce,  peas,  asparagus,  and  muskmelons  go  to  all  the 
larger  cities.  The  cotton  is  sent  to  the  manufacturing  towns  of  the 
East.  Stock  and  dairy  products  are  shipped  largely  to  the  several 
markets  on  the  Pacific  Coast. 

CLIMATE. 

The  climate  of  the  Imperial  Valley  is  decidedly  arid.  Its  chief 
characteristics  are  exceptionally  hot  summers,  with  relatively  high 
temperatures  throughout  the  entire  year;  a  low  annual  rainfall;  a 
rapid  rate  of  evaporation ;  and  a  large  percentage  of  sunshiny  days. 
The  summers  are  long  and  hot,  temperatures  of  100°  F.  or  more 
being  recorded  for  Calexico  for  every  month  from  March  to  October, 
inclusive.  During  the  months  of  May,  June,  July,  and  August  tem- 
peratures have  risen  to  117°  F.  at  that  station,  yet  so  low  is  the 
relative  humidity  that  this  degree  of  heat  is  no  more  oppressive 
than  100°  F.  in  humid  regions.  The  winters  are  short  and  mild. 
Temperatures  slightly  lower  than  32°  F.  may  be  expected  occasionally 
from  December  to  February,  inclusive.  Killing  frost  has  occurred 
at  Calexico  as  late  in  the  spring  as  March  25  and  as  early  in  the  fall 
as  Xovember  13.  The  average  date  of  the  last  killing  frost  in  the 
spring  is  reported  as  February  5,  and  that  of  the  earliest  in  the  fall 
as  December  4.  This  gives  an  average  growing  season  of  302  days, 
while  alfalfa,  many  vegetables,  and  even  strawberries  thrive  through- 
out the  winter. 

The  rainfall  is  very  light,  the  minimum  for  any  year  so  far  of 
record  being  0.64  of  an  inch.  The  average  at  Calexico  is  reported 
as  3.12  inches.    Rain  usually  comes  in  severe  storms  at  long  intervals. 


SOIL   SURVEY    OF   THE    EL   CENTRO    AREA,    CALIFORNIA. 


11 


the  irregularity  of  which  makes  rainfall  entirely  unreliable,  even  as 
a  supplement  to  irrigation. 

The    following   table    gives    the    normal    monthly,    annual,    and 
seasonal  temperatures  and  precipitation  at  Calexico,  Calif. : 

Normal  monthly  seasonal,  and  annual  temperature  and   precipitation  at 

Calexico. 


Temperature. 

Precipitation . 

Month. 

Mean. 

Absolute 
maximum. 

Absolute 
minimum. 

Mean. 

Total 

amount 

for  the 

driest  year. 

Total 
amount 
for  the  wet- 
test year. 

°F. 

52. 5 
53.7 
57.8 

°F. 
82 

78 
88 

°F. 
25 
21 
29 

Inches. 
0.04 

.28 
.80 

Inches. 
0.00 
T. 
.00 

Inches. 
0.54 

1.50 

3.76 

Winter 

54.7 

88 

21 

1.12 

T. 

5.80 

63.6 
70.0 
74.9 

100 
104 
116 

32 
41 
41 

.27 
.25 
.09 

.04 
.00 
.00 

.91 

.50 

.00 

69.5 

116 

32 

.61 

.04 

1.41 

S3. 4 
89.5 
89.6 

116 
117 
117 

54 
62 
56 

.03 
.07 
.70 

.00 
.08 
T. 

00 

July 

.03 

.00 

87.5 

117 

54 

.80 

.08 

03 

83.5 
72.3 
61.9 

110 

105 
99 

50 

42 
28 

.09 
.16 
.34 

.52 
.00 
T. 

13 

00 

1  96 

Fall 

72.6 

110 

28 

.59 

.52 

2  09 

Year 

71.6 

117 

21 

3.12 

.64 

9  33 

Strong  winds  are  of  frequent  occurrence  during  the  spring  and 
occasional  dust  storms  are  experienced  throughout  the  year.  Aside 
from  the  drifting  of  the  lighter  textured  soils  and  the  unpleasantness 
of  carrying  on  field  work  or  other  farming  operations  during  these 
storms,  the  winds  have  little  influence  on  agriculture.  The  periods  of 
high  winds  are  of  short  duration.  These  storms  are  about  the  only 
feature  to  mar  what  would  otherwise  be  an  almost  perfect  winter 
climate. 

Owing  to  the  extreme  dryness  of  the  atmosphere  and  the  intense 
sunshine  during  the  greater  part  of  the  year,  the  rate  of  evaporation 
is  very  high.  The  following  table,  compiled  from  measurements 
made  by  the  California  Development  Co.,  shows  the  average  annual 
loss  from  a  water  surface  at  Calexico,  Calif.,  for  a  3-year  period  to  be 
80.66  inches,  or  6.72  feet. 


l'J  FIELD  OPERATIONS   OF    I  III.    BUREAU    OF  SOILS,  1918. 

Evaporation  from  a  water  surface  at  Calexieo.  Cal. 


Month. 

1904 

1905 

1906 

Average 

for  three 

years. 

Inches. 
4.39 
6.32 
8.36 
9.55 
10.91 
13.89 
12.47 
10.98 
8.61 
8.78 
5.40 
3.48 

Inches. 
2.72 
1.47 
4.44 
4.74 
8.38 
12.86 
10. 43 
8.52 
7.83 
6.77 
3.23 
3.43 

Inches. 
2.57 
2.43 
5.06 
5.99 
6.84 
7.41 
6.76 
8.47 
6.73 
5.45 
3.61 
2.40 

Inches. 
3.23 

3.40 

5.94 

\pril           

6.76 

8.71 

11.39 

July             

9.89 

9.32 

7.72 

7.00 

4.08 

3.10 

103.64 

75.00 

63.66 

80.66 

AGRICULTURE. 

The  beginning  of  agriculture  in  the  El  Centro  area  was  different 
from  that  of  most  regions  in  that  it  had  a  very  definite  beginning. 
There  was  absolutely  no  agriculture  in  the  area  prior  to  1900.  It 
was  a  desert  with  no  possibility  of  crop  growing  or  stock  raising, 
because  there  was  no  water  available  for  irrigation;  but  with  the 
opening  of  the  ditches,  described  elsewhere,  agriculture  developed 
very  rapidly.  Settlers  began  to  come  into  the  Imperial  Valley  in 
1900,  but  probably  not  more  than  a  score  of  people  spent  the  sum- 
mer, or  any  considerable  part  of  it,  in  the  valley,  and  these  were 
mostly  workers  employed  in  the  preliminary  details  of  organiza- 
tion. In  the  fall  of  1900  a  large  number  of  persons  took  up  land, 
but  the  work  preliminary  to  planting  of  this  land  was  not  done  to 
any  extent  until  late  in  the  spring  of  1901,  for  the  reason  that  it 
was  impossible  before  that  time  to  say  just  when  water  would  be 
available.  About  June  of  that  year  a  small  stream  of  water  was 
brought  to  a  temporary  head  ditch  near  the  Mexican  boundary 
line,  and  with  this  water  several  fields  of  sorghum,  milo  maize, 
wheat,  and  barley  were  irrigated  that  summer,  and  experimental 
patches  of  muskmelons  and  cotton  were  grown. 

In  the  fall  of  1901,  after  the  heat  of  the  summer  was  past,  many 
more  settlers  came  into  the  area,  and  by  the  1st  of  December  some 
78,000  acres  of  land  had  been  filed  on.  Of  this  land  probably 
8,000  acres  were  being  prepared  for  cultivation.  The  water  then 
available  was  sufficient  to  irrigate  several  hundred  acres. 

In  April,  1903,  the  total  acreage  of  crops  in  the  Imperial  Valley 
was  about  25,000  acres,  nearly  all  of  which  was  within  the  area  of 


SOIL   SURVEY   OF   THE   EL   CENTRO   AREA,   CALIFORNIA.  13 

the  present  survey.  Of  this  acreage,  6,220  was  in  wheat;  14,423  in 
barley;  750  in  oats;  573  in  alfalfa ;  1,540  in  preparation  for  corn,  and 
the  rest  in  grapes  and  other  fruits,  garden  crops,  and  melons.  The 
area  planted  at  this  time  would  have  been  much  larger  had  the  irri- 
gation system  been  adequate  to  the  demands  put  upon  it. 

By  the  fall  of  1903  the  system  had  been  enlarged  and  water  was 
turned  into  many  new  ditches,  and  in  the  winter  of  1903  not  less 
than  100,000  acres  were  cropped.  In  the  fall  of  1904  the  settlers 
numbered  9,000,  and  in  the  ensuing  season  the  crops  covered  nearly 
150,000  acres.  The  products  shipped  from  the  valley  in  1909,  four 
years  later,  included  barley,  hogs,  sheep,  cattle,  dairy  products, 
honey,  wool,  asparagus,  horses,  hay,  cotton,  wheat,  cantaloupes, 
alfalfa,  meal,  grapes,  eggs,  and  poultry  (including  more  than  1,000 
turkeys),  corn,  and  small  quantities  of  other  produce. 

The  leading  crops  of  the  El  Centro  area  to-day  are  alfalfa,  cotton, 
milo  maize,  and  barley.  It  is  impossible  to  give  accurate  acreages 
for  these  crops,  for  the  area  under  consideration  is  only  a  part  of 
Imperial  County,  and  census  statistics  are  available  only  for  the 
county  as  a  whole,  and  for  the  reason  that  crops,  especially  cotton, 
grown  south  of  the  Mexican  boundary  line  are  marketed  on  this 
side  of  the  line  and  in  many  cases  are  included  in  commercial  sta- 
tistics of  the  valley. 

Often  two  crops  a  year  are  grown  on  the  same  land,  as,  for  in- 
stance, barley  followed  by  milo  or  sorghum,  and  therefore  the  total 
acreage  in  crops,  if  it  could  be  accurately  obtained,  would  be  some- 
what greater  than  the  total  acreage  of  land  under  cultivation.  The 
following  estimates,  based  on  personal  observations  and  on  statistics 
gathered  by  local  authorities  are,  however,  given  as  indicating  as 
nearly  as  possible  the  present  status  of  agriculture  in  the  area. 
Alfalfa  occupies  about  30  per  cent  of  the  tilled  land.  The  long 
growing  season,  the  existence  of  suitable  soils,  and  the  ample  supply 
of  water  give  nearly  ideal  conditions  for  this  crop.  From  five  to 
seven  cuttings  are  made  annually,  seasonal  yield  varying  from  2-| 
to  10  tons  per  acre,  4|  tons  being  a  fair  average  for  the  whole  valley.3 
A  much  larger  average  yield  could  certainly  be  obtained  with  better 
farming  methods.  Alfalfa  is  used  both  as  pasture  and  hay  for  dairy 
cattle,  and  to  a  small  extent  as  feed  for  other  cattle,  horses,  sheep,  and 
hogs.  A  considerable  proportion,  probably  25  per  cent,  is  baled 
and  shipped  from  the  valley.  During  the  winter  months  the  alfalfa 
is  not  cut  but  cattle  are  pastured  on  it.  (PI.  I,  Fig.  2.)  It  is  a  com- 
mon practice  to  sow  barley  in  seeding  alfalfa,  as  this  mixture  gives  a 
greater  yield  of  hay  for  the  first  cutting. 

3  Irrigation  of  Alfalfa  in  the  Imperial  Valley,  W.  K.  Packard.  Bulletin  284,  California 
Experiment  Station. 


14  FIELD   OPERATIONS   OF   THE   BUREAU    OF   SOILS,   1918. 

A  few  acres  of  Egyptian  cottoo  were  planted  among  the  very  first 
crops  grown  in  the  valley.  It  did  well,  hut  cotton  was  not  grown 
commercially  until  1910.  Pima  cotton,  a  variety  or  strain  of  Egyp- 
tian cotton,  was  later  introduced.  This  variety  was  bred  in  Arizona 
by  the  United  States  Department  of  Agriculture. 

Cotton  now  ranks  close  to  alfalfa  in  importance,  the  acreage  prob- 
ably approximating  35,000  acres.  (PI.  II,  Fig.  1.)  It  is  estimated 
that  half  of  this  is  occupied  by  short-staple  varieties,  12,000  acres  by 
Durango,  and  about  6,000  by  Pima, 

Land  is  prepared  for  cotton  by  plowing  during  the  winter  months 
when  the  soil  is  in  a  dry  condition.  Some  of  the  cotton  is  planted 
on  the  level  surface  but  most  of  it  on  ridges,  8|  feet  from  middle  to 
middle.  Planting  begins  with  the  Pima  in  February,  and  continues 
through  March,  April,  and  into  early  May.  The  land  is  first  irri- 
gated, by  running  the  water  down  the  furrows,  and  the  cotton  later 
planted  on  the  top  of  the  ridges.  Best  results  are  had  where  the 
cotton  is  irrigated  frequently  during  the  growing  season,  so  as  to 
maintain  uniform  moisture  conditions,  and  where  frequent  cultiva- 
tion is  given. 

The  picking  season  extends  from  the  last  of  September  to  the  time 
of  preparing  the  ground  for  the  next  crop.  A  large  proportion  of 
the  cotton  is  unpicked  by  the  first  of  the  year,  but  because  of  the 
light  rainfall  the  lint  is  not  seriously  damaged  by  standing  in  the 
field.  In  many  cases  a  second  crop  is  obtained  from  the  same  plants. 
The  stalks  are  cut  and  disposed  of  during  the  winter,  and  the  plants 
which  have  not  been  damaged  by  the  winter  renew  their  growth 
and  produce  a  crop  the  second,  year.  This  volunteer  crop  is  of 
poorer  quality  than  the  first  crop,  although  if  a  good  stand  is  ob- 
tained, the  yield  is  satisfactory. 

The  price  received  for  the  cotton  crop  of  1917  was  high,  on  ac- 
count of  war  conditions.  It  averaged  about  25  cents  a  pound  for  the 
short  staple,  35  cents  for  the  Durango,  and  75  cents  for  the  Pima. 
The  price  for  cotton  seed  was  from  $50  to  $60  a  ton.  The  crop 
averaged  about  one-half  bale  per  acre.  The  factor  which  has  lim- 
ited the  yield  for  the  last  two  years  has  been  the  shortage  of  water 
during  the  latter  part  of  the  season,  which  prevents  proper  matur- 
ing of  the  bolls. 

The  immature  bolls  ,are  picked  and  sold  separately  as  a  low-grade 
cotton. 

The  estimated  duty  of  water  for  cotton  is  reported  by  Water  Co. 
No.  1  as  2.5  acre-feet,  but  it  is  said  as  much  as  7  feet  is  sometimes 
used. 

Bermuda  grass  is  a  great  pest  in  the  cotton  fields.  It  is  brought 
in  by  the  water,  as  the  banks  of  the  ditches  are  in  many  places 
covered  with  this  grass. 


SOIL   SURVEY   OF   THE   EL  CENTRO   AREA,   CALIFORNIA.  15 

The  cotton  is  sold  through  local  associations  or  to  buyers  who 
visit  the  area.  Most  of  it  goes  to  New  Orleans  wholesale  houses.  A 
number  of  large  gins  are  located  in  the  towns  of  the  area,  and  the 
seed  is  sent  to  the  oil  mills  at  El  Centro  and  Calexico.  Cotton  grow- 
ing the  past  season  has  been  very  profitable,  owing  to  the  ruling  high 
prices,  and  an  increased  acreage  is  being  planted  in  1918.  It  is 
probable  that  when  normal  conditions  return  and  prices  fall  other 
lines  of  agriculture  will  be  found  more  profitable  in  the  valley  and 
that  cotton  growing  will  give  way  to  a  certain  extent  to  other  crops. 

Nearly  25  per  cent  of  the  tilled  land  is  in  milo.  This  crop  is  sown 
from  May  15  to  September  1  and  ripens  in  90  to  100  days.  Often  two 
crops  a  year  are  grown.  The  average  yield  of  grain  is  about  three- 
fourths  ton.  One  ton  is  considered  a  good  yield,  but  as  much  as  2i 
tons  have  been  obtained.  The  crop,  both  thrashed  and  unthrashed, 
is  fed  to  hogs  and  other  stock.  The  grain  is  shipped  out  of  the 
valley  in  large  amounts. 

Barley  is  the  fourth  crop  in  importance,  about  20  per  cent  of  the 
cultivated  area  being  given  to  it.  It  is  sown  in  the  early  winter  and 
harvested  in  April.  The  average  yield  is  14  sacks  per  acre,  with  a 
range  from  10  to  25  sacks.  Most  of  the  barley  is  shipped  from  the 
^area.  A  crop  of  barley  is  often  followed  by  a  crop  of  milo  the  same 
year. 

The  main  factor  which  has  brought  about  the  development  of  truck 
growing  in  the  area  is  the  extreme  earliness  of  the  season,  which  makes 
it  possible  to  place  the  products  on  the  markets  of  the  country  well 
ahead  of  the  products  from  any  other  large  truck-producing  region 
in  the  United  States.  For  instance,  the  first  lettuce  is  shipped  during 
Christmas  week  and  the  bulk  of  the  crop  is  marketed  by  March. 
Truck  crops  probably  occupy  from  5  to  8  per  cent  of  the  tilled  land 
of  the  El  Centro  area.  This  is  not  a  large  acreage  compared  with 
the  leading  crops,  but  the  fact  that  these  are  intensive  crops  and 
large  yields  and  large  returns  per  acre  are  obtained  gives  these  crops 
an  importance  much  greater  than  their  acreage  would  indicate.  The 
crops,  in  the  order  of  their  importance,  are  as  follows:  Muskmelons, 
lettuce,  peas,  strawberries,  asparagus,  tomatoes,  onions,  and  beans. 
California  produces  more  muskmelons  than  any  other  State  in  the 
Union,  and  about  one-third  of  the  California  product  is  grown  in 
this  area.  The  truck  crops  are  shipped  by  express  and  in  carload 
lots  to  all  the  main  markets  of  the  United  States.  Japanese  grow 
most  of  these  crops. 

Table  grapes,  dates,  and  apricots  do  well  in  the  area  and  are  grown 
in  a  small  way  commercially.  There  are  a  few  small  groves  of  grape- 
fruit and  oranges,  but  plantings  of  any  fruit  are  apparently  not 
being  made  to  any  extent. 


16  rir.l  I'   OPERATIONS   OF   THE  BUREAU  OF  SOILS,  1918. 

Sudan  grass  is  a  promising  new  crop.  It  is  an  annual  and  can  be 
grown  in  a  50-day  period  after  other  crops  have  been  taken  off  the 
ground.  Sorgo  (saccharine  sorghum)  is  also  a  new  crop  that  is 
receiving  attention.  Large  yields  have  been  obtained  in  experimental 
fields  and  a  large  acreage  will  be  planted  during  the  corning  season. 
It  is  best  utilized  as  ensilage  for  dairy  cattle. 

Wheat  and  oats  are  being  advised  by  the  farm  centers  to  take  the 
place  of  barley,  and  they  are  increasing  rapidly  in  acreage. 

Dairying  is  one  of  the  more  important  industries  in  the  area. 
Green  feed  is  obtainable  all  the  year  round,  and  costly  buildings  are 
not  needed.  Some  of  the  dairymen  provide  barns,  others  only  open 
shelters.  Shade  should  always  be  furnished.  Alfalfa  is  the  main 
feed,  but  it  is  supplemented  with  barley,  milo,  and  pasturage  in  the 
cotton  fields.  All  the  leading  breeds  of  dairy  cattle  are  found  in  the 
valley,  and  in  many  cases  the  herds  comprise  excellent  stock.  Hol- 
stein  cattle  are  the  most  numerous.  There  are  creameries  at  El 
Centro,  Heber,  Holtville.  Calexico,  and  Imperial.  These  handle  most 
of  the  milk;  very  little  butter  is  made  in  private  dairies.  At  the 
present  time  (1918)  many  are  going  out  of  the  dairy  business,  owing 
to  the  high  price  of  labor  and  feed  and  the  relatively  low  price  of 
butter  fat. 

Cattle  and  sheep  are  shipped  into  the  valley  from  other  parts  of 
the  State  and  from  other  States,  mainly  during  the  winter  months, 
to  be  fattened  for  the  market.  The  numbers  of  beef  cattle  and  sheep 
are  increasing  each  year.  Imperial  County  is  said  to  lead  the  State 
in  the  production  of  hogs.  Many  carloads  of  hogs,  from  seven  to 
eight  months  old.  are  sent  out  of  the  valley  to  the  farms  of  the  Middle 
West,  there  to  be  fattened  on  corn  before  reaching  the  final  market. 
The  mild  weather  during  the  farrowing  season  and  the  abundance  of 
green  feed  make  it  possible  to  raise  stock  hogs  very  cheaply. 

Large  quantities  of  poultry,  especially  turkeys,  are  raised  in  the 
area.  Holtville  is  the  center  of  this  industry.  In  October  and  No- 
vember, 1917,  more  than  $40,000  worth  of  turkeys  were  shipped  from 
that  station.  During  a  single  week  the  shipment  of  eggs  from  this 
point  has  reached  83,000  dozen. 

The  farmers  find  that  barley  and  alfalfa  are  quite  resistant  to 
alkali,  and  these  crops  are  grown  where  other  crops  would  fail  be- 
cause of  the  excess  of  soluble  salts  in  the  soil.  Barley  will  give 
greater  returns  on  the  clay  soils  than  will  alfalfa.  Cotton  is  grown 
on  soils  of  a  wide  variety  of  textures,  but  it  is  found  that  alfalfa  will 
make  a  crop  on  the  lightest  soils  when  cotton  is  a  failure. 

The  farming  methods  characteristic  of  irrigated  sections  are  prac- 
ticed in  the  area.  Tractors  are  used  in  plowing  and  preparing  the 
land  for  crops.  Their  number,  already  large,  is  increasing.  Small 
tractors  for  the  cultivation  of  cotton  are  being  introduced. 


Report  of  Bureau  of  Soils,  U.  S.  Dept.  of  Agriculture,  1918. 


Plate  I. 


Photo  from  Univ.  of  California. 

FIG.     I. — VIEW    NEAR    HOLTVILLE   SHOWING    GORGE   OF    ALAMO    RIVER. 

The  perpendicular  banks  give  an  excellent  exposure  of  the  deposits  of  the  Colorado  River, 
showing  their  definite  stratification.    The  soil  here  is  the  Imperial  silty  clay. 


Photo  from  Univ.  of  California. 

Fig.  2. — Cattle  Grazing  on  Alfalfa  in  Winter  Season. 

Wintering  stock  on  alfalfa  is  an  important  feature  of  the  stock-raising  industry  in  this  valley. 


of  Soils,  U.  S.  Dept.  of  Agriculture,  1918. 


Plate   II. 


Fig.   I. — Cotton  Stored  in  Yard  at  Imperial. 


3     *.      f: 


Fig.    2. — Topography    and    Characteristic    Surface    Gravel 
pavement)  on  superstition  gravelly  sand. 


Desert 


SOIL  SURVEY   OF   THE   EL  CENTRO   AREA,   CALIFORNIA.  17 

As  a  whole  the  farms  are  well  equipped  with  stock  and  the  best 
machinery,  but  in  many  cases  the  farm  buildings  are  of  a  temporary 
character.  This  is  especialty  true  of  the  buildings  on  rented  farms. 
Barns  and  sheds  for  stock  are  of  very  open  construction  or  are  lack- 
ing entirely.  The  average  dwelling  house  is  built  mainly  with  the 
idea  of  being  cool  in  summer.  Silos  have  been  built  in  large  num- 
bers during  the  last  two  years. 

So  far  no  definite  crop  rotations  have  been  worked  out  by  the 
farmers.  The  country  is  quite  new,  and  the  soil  shows  no  sign  of 
exhaustion,  and  silt  is  continually  brought  in  and  deposited  by  the 
irrigation  water,  which  has  a  tendency  to  renew  the  soil.  No  com- 
mercial fertilizers  are  used.  In  the  case  of  the  lighter  soils,  which 
are  low  in  organic  matter,  it  is  found  advisable  to  use  stable  or  green 
manures. 

In  winter  there  is  an  abundance  of  farm  labor,  but  in  summer, 
when  there  is  more  work  to  be  done,  much  of  the  labor  has  left  the 
valley  to  escape  the  heat.  At  the  time  of  this  survey  farm  labor  in 
winter  was  paid  from  $40  to  $55  a  month  and  board,  and  good 
milkers  received  $65  a  month.  In  the  summer  monthly  wages 
reached  $70  or  $80  and  good  milkers  were  paid  from  $90  to  $100 
with  board.  Day  labor  in  winter  received  from  $2  to  $2.50  a  day 
and  board,  and  in  summer  $3  to  $3.50  a  day  with  board. 

The  price  paid  for  picking  cotton  at  the  time  of  this  survey  was 
from  $1.25  to  $2  a  hundred  pounds  for  the  short  staple;  from  $1.50 
to  $2.50  for  the  Durango ;  and  from  $2  to  $3.50  for  the  Pima  cotton. 
The  Pima  cotton  has  smaller  bolls,  making  the  picking  slower  and 
harder. 

Most  of  the  farm  labor  is  American.  Negroes  are  employed 
largely  in  the  cotton  fields.  Hindus  are  occasionally  employed  by 
the  month,  but  usually  prefer  to  do  contract  labor,  such  as  picking 
cotton  or  heading  milo.  Mexicans  are  employed  to  some  extent  on 
the  larger  ranches  and  on  contract  work,  but  are  not  usually  hired 
by  the  month  on  the  smaller  farms.  Japanese  laborers  are  important 
in  the  production  of  fruit  and  garden  truck,  especially  muskmelons. 
They  usually  work  by  contract,  being  rarely  employed  by  the  month 
by  Americans.  Laborers  from  southern  Europe  are  becoming  an 
important  factor,  especially  in  the  dairy  and  hog  business. 

Investigations  by  the  farm  centers  in  the  area  indicate  that  the 
average  size  of  the  farm  is  90  acres.  There  are  no  5  and  10  acre 
farms,  but  there  are  many  40  to  60  acre  farms,  and  there  are  several 
farms  that  contain  more  than  1,000  acres. 

Probably  a  little  over  one-half  of  the  farms  are  operated  by  the 
owners,  but  in  the  case  of  cotton  apparently  more  than  half  the  crop 
•58142°— 22 3 


Is  llKLD  OPERATIONS   OF   THE   BUREAU    OF  SOILS,  1918. 

ia  grown  by  tenants.  Of  these  tenants,  about  one-tenth  arc  negroes, 
one-fifth  Hindus,  ami  the  rest  native  whites.  Very  few  Mexicans  or 
Japanese  grow  cotton. 

SOILS. 

The  soils  of  the  El  Centro  area  are  all  so  young  that  they  do  not 
differ  greatly  from  the  geological  formations  which  make  up  the  sur- 
face deposits  of  the  region.  Very  little  progress  has  been  made  in 
soil  development.  On  account  of  the  extreme  desert  conditions  which 
existed  in  the  region  until  a  very  few  years  ago  there  was  so  slight  a 
covering  of  native  vegetation  that  the  accumulation  of  organic  mat- 
ter in  the  surface  soil  was  veiy  slight.  The  surface  soils  and  the  sub7 
soils  are,  in  this  respect,  very  much  alike.  In  some  cases  the  sur- 
face soil  is  slightly  darker  than  the  subsoil,  but  this  is  not  universal, 
so  that  as  a  whole  it  can  be  said  that  very  little  progress  in  the  de- 
velopment of  a  surface  soil  with  an  important  constituent  of  organic 
matter  has  been  made. 

As  will  be  brought  out  in  the  description  of  the  soils,  the  horizons 
found  in  them  are  horizons  of  deposition  rather  than  those  of  soil  de- 
velopment. They  are  geological  horizons,  strictly  speaking,  rather 
than  soil  horizons,  although  it  should  be  borne  in  mind  in  this  con- 
nection that  soils  and  geological  formations  are  identical  at  the 
period  of  time  when  deposition  of  material  in  a  given  area  has 
stopped  or  become  slow  enough  to  permit  the  growth  of  plants.  The 
stage  of  development  of  the  soils  of  the  El  Centro  area  has  passed 
but  little  beyond  this  most  primitive  stage. 

The  presence  in  the  soil  of  a  small,  often  very  small,  percentage  of 
soluble  salts  seems  to  cause  the  development  of  well-defined  soil  hori- 
zons at  an  early  stage  in  their  development.  An  amount  of  salts 
sufficient  for  such  development  is  unquestionably  present  in  a  large 
part  of  this  area,  but  on  account  of  the  extremely  recent  deposition 
of  the  soil  material  it  is  rather  difficult  to  determine  in  many  cases 
whether  the  presence  of  a  heavy  subsurface  horizon  is  due  to  deposi- 
tion or  to  soil  development.  It  is  clear,  however,  that  the  develop- 
ment has  not  gone  far  enough  to  warrant  the  separation  of  the  soils 
on  this  basis.  They  have  been  differentiated,  therefore,  on  the  basis 
of  features  that  have  been  inherited  from  the  geological  character  of 
the  material  itself  or  from  conditions  of  deposition.  These  features 
and  conditions  are  described  below. 

The  area  occupied  by  the  Colorado  Desert  is  mainly  an  old  struc- 
tural valley  which  has  been  partly  filled  b}^  accumulations  of  sedi- 
ments transported  by  waters  of  the  short  drainage  courses  having 
their  sources  in  the  surrounding  mountains  and  by  the  finer  sedi- 
ments carried  into  it  by  the  Colorado  River.  The  slopes  of  the 
surrounding  mountains  are  steep,  rugged,  and  often  greatly  eroded 


SOIL  SURVEY   OF   THE  EL  CENTRO   AREA,   CALIFORNIA.  19 

and  their  bases  are  commonly  buried  beneath  upturned  and  eroded 
strata  of  conglomerate,  sandstone,  and  clay;  by  masses  of  recent 
talus  material;  or  by  the  short,  steep  alluvial  fans  formed  at  the 
mouths  of  the  smaller  water  courses.  Beyond  these  steeper  basal 
slopes,  the  floor  of  the  desert  slopes  more  gradually  toward  the 
lowest  part  (Salton  Sink)  of  the  depression,  and  presents  a  rather 
uniform  surface  broken  only  by  the  presence  of  an  occasional  desert 
stream  course,  by  more  or  less  extensive  and  prominent  masses  of 
wind-blown  sand,  or  by  a  few  occurrences  of  igneous  and  old  sedi- 
mentary material  that  are  now  largely  buried  beneath  the  detrital 
material  forming  the  present  desert  floor. 

A  large  part  of  this  region  lies  at  or  below  sea  level,  and  the 
approximate  area  of  this  depression  is  quite  clearly  outlined  for  a 
considerable  part  of  the  distance  by  a  low  sandy  and  gravelly  ridge 
which  marks  the  level  and  the  shore  line  of  the  lasf  body  of  water 
that  covered  this  area  for  a  considerable  period,  of  time. 

Following  the  uplift  of  the  mountain  masses  surrounding  this 
region  on  the  north  and  west,  there  was  a  considerable  period  of 
erosion,  during  which  there  was  deposited  along  the  base  of  the 
mountains  an  extensive  area  of  sands,  gravels,  and  clays.  At  a  con- 
siderably later  period  this  mass  of  sediment,  now  in  the  form  of  more 
or  less  thoroughly  consolidated  conglomerates,  sandstones,  and  clays, 
was  nearty  everywhere  subjected  to  a  series  of  movements  by  which 
they  were  greatly  tilted,  faulted,  and  folded.  In  that  condition  they 
were  subjected  to  erosion,  probably  for  a  considerable  period,  during 
which  large  portions  were  removed  and  the  remaining  portions 
carved  into  a  typical  bad-land  topography.  A  period  followed  that 
of  the  erosion,  during  which  these  masses  were  buried  beneath  a  vast 
amount  of  coarser  and  more  recent  alluvial  material  which,  at  the 
present  time,  forms  the  floor  of  the  desert  above  the  old  beach  line. 
Coincident  with  this  deposition  of  material  by  the  mountain  streams, 
the  Colorado  River  was  depositing  beds  of  fine  sand,  silt,  and  clay 
in  that  part  of  the  basin  below  sea  level,  and  gradually  filled  the 
depression  to  about  its  present  level.  Eventually  the  Colorado  River 
was  diverted  toward  the  Gulf  of  California  by  the  slow  development 
of  a  delta  ridge,  and  the  waters  north  of  that  obstruction  gradually 
disappeared  by  evaporation.  Since  that  time  the  Colorado  River  has 
occasionally  broken  through  the  barrier  and  flowed  into  the  Salton 
Sink  for  short  periods,  but  such  overflows  have  had  little  effect  upon 
any  large  areas  of  the  soils  already  present  within  the  area  of  this 
survey. 

Since  the  last  great  period  of  deposition  of  materials  about  the 
mountain  bases,  there  has  been  some  local  erosion  by  streams  from 
the  eastern  front  of  the  Peninsula  Range,  and  in  restricted  areas 


•JO  FIELD   OPERATIONS   OF   THE  BUREAU   OF   SOILS,  1018. 

the  coarser  surface  material  has  been  entirely  removed  and  the  old 
upturned  sediments  exposed  and  subjected  to  still  further  erosion. 
Examples  of  this  are  to  be  seen  on  many  of  the  lower  slopes  of 
the  outliers  of  the  main  range  of  mountains  and  in  the  vicinity  of 
Yuha  Buttes.  In  the  latter  region,  not  only  has  the  overlying  man- 
tle of  later  unconsolidated  sedimentary  materials  been  removed,  but 
the  exposed  underlying  strata  of  clay  and  concretionary  sandstone 
have  been  subjected  to  erosion,  leaving  a  very  rugged  area  of  low 
relief,  almost  entirely  barren  of  even  the  usual  desert  vegetation. 

Within  the  limits  of  the  El  Centro  area,  none  of  the  igneous  for- 
mations composing  the  larger  part  of  the  adjacent  mountain  ranges 
are  found,  but  the  old  upturned  sediments  occur  over  an  area  of 
several  square  miles,  particularly  in  the  southwestern  part  of  the 
area  and  locally  elsewhere.  These  form  no  areas  of  arable  land, 
and  are  largely*  represented  upon  the  soil  map  by  Kough  broken 
land. 

The  more  recent  unconsolidated  sedimentary  materials  compose 
the  larger  part  of  the  desert  soils  above  the  beach  line  along  the 
eastern  and  western  margins  of  the  area.  These  sediments  form  a 
gently  rolling  plain  sloping  toward  the  central  part  of  the  area, 
the  surface  of  which  is  broken  by  occasional  desert  stream  ways  and 
liv  bodies  of  wind-blown  sand.  Below  the  beach  line  the  materials 
are  largely  lacustrine  deposits  of  fine  sand,  silt,  and  clay,  some  of 
which  have,  however,  been  redistributed  or  modified  by  winds  or 
streams.  Usually  these  deposits  occur  in  a  series  of  strata  extend- 
ing to  unknown  depths. 

In  mapping  the  soils  of  the  El  Centro  area,  a  difficulty  not  usually 
found  was  encountered.  Only  occasionally  is  the  subsoil  composed 
entirely  of  material  of  uniform  texture.  In  most  places  it  is  made 
up  of  several  sharply  defined  strata  of  varying  textures,  rarely  with 
any  regularity  in  vertical  distribution.  Oftentimes  they  consist  of 
dovetailing  lens-shaped  deposits,  any  one  stratum  extending  but  a 
short  distance  horizontally.  As  a  result  of  these  irregularities,  it 
is  practically  impossible  to  indicate  in  detail  accurately  upon  the 
soil  map  the  variations  in  texture  of  the  subsoils  of  the  various  types 
of  soil.  The  texture  of  the  surface  soils,  which  is  indicated  by  the 
latter  part  of  the  type  name,  is  indicated  upon  the  soil  map  as 
closely  as  possible,  taking  the  scale  of  the  map  into  consideration, 
and  also  the  fact  that  the  changes  in  texture  are  usually  gradual 
and  that  a  definite  boundary  as  indicated  upon  the  map  is  usually 
but  an  approximation. 

The  heavier  textured  materials  are  compact,  locally  indurated,  are 
frequently  of  joint  structure,  and  occasionally  show  the  concentra- 
tion of  calcareous  material  or  alkali  salts  along  cracks  and  joint 
planes.     Since  their  deposition  the  lighter  textured  materials  have 


SOIL  SURVEY  OF   THE  EL  CENTRO   AREA,   CALIFORNIA.  21 

been  transported  and  reworked  by  wind  action,  resulting  in  either 
the  removal  of  the  original  material,  forming  what  is  known  as 
"blow-outs,"  or  in  the  building  up  of  accumulations  of  wind-blown 
sands,  forming  extensive  areas  of  Dunesand. 

The  materials  from  which  the  soils  of  this  area  are  formed  are 
divided  into  three  main  groups:  (a)  Old  valley-filling  materials,  (h) 
aeolian  or  wind-laid  materials,  (c)  recent  alluvial  fan  and  flood-plain 
deposits.  No  residual  soil  materials  from  consolidated  rocks  occur 
within  the  limits  of  the  area. 

The  old  valley-filling  deposits,  which  are  by  far  the  most  extensive, 
cover  more  than  66  per  cent  of  the  area  surveyed.  The  aeolian  mate- 
rials occupy  about  25  per  cent  of  the  area,  and  the  recent  alluvial 
materials  are  of  small  extent,  occupying  less  than  3  per  cent  of  the 
area.  Each  of  these  groups  may  include  a  number  of  soil  series  and 
types  that  differ  in  color,  texture,  structure,  and  topography,  but  are 
alike  in  their  methods  of  formation.  The  soil  series  is  represented 
by  one  or  more  soil  types  alike  in  essential  features  of  origin,  mode 
of  formation,  and  color,  but  differing  from  the  others  in  texture. 

Old  valley-filing  soils. — The  old  valley-filling  soils  are  derived  from 
old  alluvial  or  sedimentary  materials.  These  have  undergone  more 
or  less  modification  by  weathering  and  leaching  since  their  deposi- 
tion. The  soil  types  are  normally  characterized  by  rather  compact 
subsoils,  in  which  there  may  be  accumulations  of  calcium  or  other 
minerals,  forming  cemented  hardpans  or  causing  a  mottled  color.  In 
the  present  survey  little  if  any  cemented  hardpan  occurs,  but  some 
of  the  subsoils  carry  thin,  irregular  seams  or  layers  of  material 
cemented  with  lime,  and  in  many  places  the  subsoil  of  the  heavier 
types  is  so  compact  that  it  forms  an  effective  barrier  to  the  movement 
of  moisture.  The  topography  of  these  soils  varies  from  level  to 
moderately  rolling.  The  drainage  is  somewhat  restricted  in  the 
heavier  members.  Locally  these  soils  support  a  scattering  growth  of 
mesquite  trees,  but  for  the  larger  part  they  have  only  a  scanty 
growth  of  shrubs  and  bushes.  Local  areas  are  devoid  of  vegetation. 
The  group  includes  in  this  survey  both  the  soils  derived  from  old 
lateral  stream-laid  and  alluvial-fan  deposits,  lying  on  marginal  slopes 
of  the  valley,  and  the  soils  derived  from  lacustrine  or  lake-laid  sedi- 
ments and  associated  stream-laid  deposits  occurring  below  the  beach 
line.  These  have  been  grouped  in  four  series,  the  Imperial,  Holt- 
ville,  Tijeras,  and  Superstition. 

The  surface  soils  of  the  types  included  in  the  Imperial  series  are 
in  color  prevailingly  light  brown  to  chocolate  brown  with  a  pro- 
nounced pinkish  or  purplish  tint.  The  subsoil  may  be  either  some- 
what darker  or  lighter  colored  than  the  surface  soils,  and  is  in  places 
slightly  mottled  with  grayish  or  reddish  stains.     It  is  predominantly 


82  FIELD    OPERATIONS   OF    THE   BUREAU    OF    BOILS,    li>18. 

heavy  :nul  shows  slinlv  or  jointed  structure  and  is  very  compact,  but 
no  cementing  of  the  soil  particles  has  taken  place.  Concentrations  of 
lime  are  not  visible,  but  the  surface  soil  and  subsoil  effervesce  freely 
with  acid,  indicating  the  presence  of  appreciable  amounts  of  this 
material.  This  series  is  extensively  developed  throughout  the  area 
under  the  existing  canals  and  small  bodies  of  it  lie  on  the  desert 
west  of  the  Main  West  Side  Canal.  In  this  area  bodies  of  soil,  to  a 
large  extent  wind  blown  or  wind  altered,  too  small  to  be  shown  on  the 
soil  map,  have  been  included.  The  series  differs  from  the  related 
Holtville  series  by  the  heavier  and  more  compact  subsoil. 

The  materials  of  which  the  Imperial  soils  are  composed  consist  of 
sediments  deposited  by  the  Colorado  River.  These  have  been  derived 
from  many  different  kinds  of  igneous  and  sedimentary  rocks  occupy- 
ing the  drainage  basins  of  that  stream  and  its  tributaries. 

Three  types  of  the  Imperial  series  are  identified  in  the  present 
survey,  the  silt}'  clay  loam,  silty  clay,  and  clay. 

The  surface  soils  of  the  types  included  in  the  Holtville  series  are 
similar  in  texture,  structure,  and  color  to  those  of  the  Imperial  series, 
i.  e..  they  are  prevailingly  light  pinkish  or  purplish  brown  to  dark 
chocolate  brown  in  color,  heavy  in  texture,  compact,  uniformly 
calcareous,  and  have  a  smooth  level  surface.  This  series  differs  from 
the  Imperial  series  in  having  a  lighter  and  more  open  subsoil  which 
is  typically  a  fine  sandy  loam  or  fine  sand.  Heavier  textured  ma- 
terials in  the  subsoil  occur  only  as  included  thin  lenses  or  layers  or 
in  areas  of  such  small  extent  that  they  can  not  be  satisfactorily  shown 
upon  a  map  of  the  scale  used  in  this  survey. 

The  materials  of  which  this  series  of  soils  is  composed  have  been 
derived  from  a  wide  range  of  igneous  and  sedimentary  rocks  lying 
within  the  watershed  of  the  Colorado  River. 

Four  types  of  the  Holtville  series  are  mapped  in  the  El  Centro 
area,  the  very  fine  sandy  loam,  silty  clay  loam,  silty  clay,  and  clay. 

In  typical  areas  the  Tijeras  series  includes  types  with  light  grajTish 
red  or  pale-red  to  light-pinkish  or  purplish-brown  color.  As  mapped 
in  this  survey,  however,  there  are  included  areas  in  which  the  surface 
soil  is  a  light-grayish  or  grayish-brown  color,  in  places  approaching 
that  of  the  Superstition  soils.  The  subsoil  is  typically  of  a  light 
brownish  red,  pale-red,  or  pinkish  color,  somewhat  lighter  than  that 
of  the  surface  soil.  Locally  the  color  is  pinkish  or  purplish  gray  or 
light  grayish  brown.  The  upper  part  of  the  soil  carries  a  large 
quantity  of  waterworn  gravel  composed  of  many  different  kinds  of 
rocks,  and  on  undisturbed  areas  this  may  cover  the  surface.  The 
mass  of  the  soil,  however,  contains  only  a  small  proportion  of  gravel. 
The  subsoil  is  quite  compact  and  in  many  places  heavier  than  the 
soil.  Both  soil  and  subsoil  are  highly  calcareous,  the  latter  in  many 
places  including  concretions,  seams,  or  layers  of  lime.     The  sub- 


SOIL   SURVEY    OF    THE    EL   CENTRO    AREA,    CALIFORNIA.  23 

stratum  occurring  from  3  to  10  feet  below  the  surface,  normally  con- 
sists of  very  old  deposits  of  stratified  heavy  clay  and  sandstone-like 
layers  or  concretions  inclined  at  a  sharp  angle,  but  in  some  areas  the 
materials  below  the  subsoil  are  similar  to  those  beneath  the  Super- 
stition and  include  coarse  sandy  deposits  of  open  structure.  This 
series  is  confined  to  the  southwestern  part  of  the  area  surveyed  and 
occurs  mainly  above  the  old  beach  line. 

The  materials  giving  rise  to  the  soils  of  this  series  are  old  sedi- 
mentary deposits.  The  substratum  consists  of  lacustrine  or  other 
water-laid  sediments  that  have  been  tilted  and  more  or  less  con- 
solidated since  their  deposition. 

The  soils  of  this  series  in  this  survey  occur  largely  on  an  elevated 
mesa,  in  the  southwestern  portion  of  the  area,  and  only  a  few  bodies 
of  it  lie  on  the  lower  parts  of  the  desert.  The  topography  varies 
from  smooth  and  uniform  to  somewhat  rolling,  and  is  marked  by 
shallow  drainage  courses.  The  soils  of  this  area  are  treeless,  and 
parts  of  them  are  devoid  of  vegetation. 

Only  one  type  of  this  series,  the  gravelly  fine  sandy  loam,  has 
been  recognized  in  the  present  survey. 

Both  soil  and  subsoil  of  the  Superstition  series  are  light  gray  or 
light  brownish  gray.  The  soils  lack  uniformity,  owing  to  the  method 
of  their  formation.  The  subsoil,  though  in  places  uniform  in  texture 
and  structure  to  a  depth  of  several  feet,  is  more  commonly  made  up 
of  variable  strata  of  sand,  fine  sand,  fine  sandy  loam,  and  here  and 
there  fine  gravel.  There  is  no  regularity  in  the  arrangement  of  these 
strata  in  the  profile.  The  subsoil  is  somewhat  more  compact  than 
the  soil,  but  is  characteristically  porous  and  the  soils  low  in  power  to 
hold  water.  Waterworn  gravel  is  nearly  always  present  on  the  sur- 
face. (PI.  II,  Fig.  2.)  The  subsoil  is  in  places  gravel  free,  but  in 
others  it  occurs  usually  in  thin,  irregular  strata. 

Both  soil  and  subsoil  are  highly  calcareous,  and  accumulations  of 
lime  exist  in  the  subsoils  of  several  of  the  types,  either  in  irregular 
strata  or  in  rather  large  masses.  The  soils  of  this  series  are  derived 
from  slightly  weathered  old  valley-filling  materials  accumulated  in 
alluvial  fan  and  desert-wash  deposits.  The  materials  come  originally 
from  many  different  kinds  of  rocks.  In  this  area  the  materials  in- 
clude sandy  and  gravelly  deposits  occupying  bars  and  beaches  mark- 
ing former  shore  lines  of  an  inland  lake  or  sea. 

Soils  of  this  series  occur  in  the  desert  east  and  west  of  the  present 
irrigated  area,  the  most  extensive  bodies  lying  in  the  latter  district. 

The  surface  varies  from  very  uniformly  smooth  and  gently  sloping 
to  moderately  rolling.  It  has  been  subject  to  local  erosion  by  inter- 
mittent streams.  Surface  drainage  is  well  developed  and  the  sub- 
drainage  is  excessive.  The  areas  arc  treeless,  the  only  vegetation  be- 
ing a  scattered  growth  of  shrubs  and  cacti. 


24  FIELD  OPERATIONS   OF   THE    BUREAU    OF   SOILS,  1918. 

hi  the  El  Centro  area  the  gravelly  coarse  sand,  gravelly  sand, 

coarse  sand,  and  fine  sand  of  the  series  are  mapped. 

Wind-laid  soils. — Since  the  disappearance  of  the  former  lake  the 
lighter  textured  surface  materials  have  been  subjected  to  modification 
by  winds  of  relatively  high  velocities.  The  soils,  where  not  protected 
by  some  system  of  cropping,  are  still  being  reworked  by  that  agency. 
The  result  is  that  all  of  the  lighter  textured  materials,  with  one  ex- 
ception, have  either  been  transported  for  unknown  distances  or  else 
modified  sufficiently  to  be  classified  with  wind-laid  materials. 

The  surface  soils  of  the  types  in  this  group  are  either  grayish 
brown  or  light  purplish  or  pinkish  brown.  They  are  loose  and  in- 
I  coherent,  except  where  they  grade  into  some  of  the  heavier  types  of 
the  Imperial  or  Holtville  series.  The  subsoil  is  like  that  of  the  Im- 
perial or  Holtville  soils.  When  of  a  heavy  texture  the  subsoil  shows 
definite  stratification,  but  this  may  not  be  apparent  in  the  lighter 
textured  materials.  Owing  to  this  variation  in  the  character  of  the 
subsoil  the  profile  is  not  everywhere  typical  and  there  are  included 
variations  which,  if  occurring  in  large,  areas,  would  have  been 
mapped  as  some  other  type.  Fine  waterworn  gravel  is  present  in 
some  of  the  types,  either  distributed  through  the  soil  profile  or  occur- 
ring only  on  the  surface.  The  topography  is  seldom  smooth.  In 
/  most  places  it  consists  of  low  dunes  and  undulations.  In  many  cases 
the  surface  material  has  been  removed  by  the  wind,  forming  what  is 
known  as  "  blow-outs.'" 

Soils  of  this  group  in  places  support  a  scattered  growth  of  mes- 
quite  trees,  but  over  the  larger  part  of  this  area  the  vegetation  either 
consists  of  a  few  desert  shrubs  or  is  entirely  wanting. 

The  material  is  of  loose  porous  structure  and  drainage  is  excessive, 
except  wdiere  underlain  at  shallow  depth  by  compact  heavy  sediments. 

Two  series  of  soils  in  this  group  have  been  mapped  in  the  El  Centro 
area.    These  are  named  the  Meloland  and  Kositas  series. 

The  soils  of  the  types  included  in  the  Meloland  series  are  light 
grayish  brown  to  purplish  or  chocolate  brown.  The  subsoil  is  identi- 
cal with  that  of  the  Imperial  series.  The  surface  is  hummocky  to 
rolling,  and  small  isolated  areas  are  sufficiently  uneven  to  be  classed 
as  Dunesand.  The  drainage  conditions  are  variable,  depending  upon 
the  depth  to  the  heavier  subsoil  or  substratum.  Both  soil  and  subsoil 
are  calcareous,  and  the  heavier  textured  members  often  carry  ap- 
preciable quantities  of  alkali.  Three  types  are  shown  on  the  map, 
the  gravelly  sand,  fine  sand,  and  fine  sandy  loam. 

The  types  included  in  the  Eositas  series  have  surface  soils  identical 
with  those  of  the  Meloland  series  in  color,  texture,  structure,  and 
topography,  but  their  subsoil  differs  from  that  of  the  latter  series,  and 


SOIL   SURVEY   OF   THE   EL   CENTRO   AREA,   CALIFORNIA.  25 

the  separation  is  made  on  this  basis.  The  Rositas  subsoil  consists  of 
sand,  fine  sand,  and  fine  sandy  loam,  is  permeable,  and  does  not  show 
stratifications,  although  believed  to  be. either  old  alluvial  or  lake-laid 
sediments  as  they  were  deposited  by  the  Colorado  River  or  in  the 
waters  of  the  lake,  or  of  these  materials  more  or  less  redistributed  by 
winds. 

.  The  drainage  of  these  soils  is  excessive,  and  it  is  only  along  the 
margins  of  the  types,  where  they  grade  into  the  heavier  members  of 
some  of  the  other  series  or  where  seepage  from  the  canals  occurs,  that 
there  is  any  alkali  present. 

Five  types  of  Rositas  series  are  mapped  in  this  survey — the  Rositas 
sand,  gravelly  fine  sand,  fine  sand,  very  fine  sand,  and  very  fine  sandy 
loam. 

Recent  alluvial  soils. — The  recent  alluvial  soils  include  a  number  of 
small,  irregular  areas  along  the  flood  plains  of  New  River,  and  some  ' 
rather  extensive  alluvial  fans  on  the  desert  slopes.  In  the  former  I 
location  the  soils  have  been  deposited  by  New  River  since  the  forma- 
tion of  the  present  New  River  wash  (1905-6),  and  are  still  subject 
to  change  through  the  occasional  addition  of  material  deposited  dur- 
ing periods  of  overflow.  They  are  also  locally  receiving  considerable 
quantities  of  wind-blown  materials  from  adjacent  areas  of  sand  and 
fine  sand  soils. 

Owing  to  the  small  extent  of  the  individual  bodies  of  these  alluvial 
soils  along  the  New  River,  to  the  many  abrupt  changes  in  texture  from  I 
place  to  place,  and  to  the  fact  that  areas  are  not  used  for  agriculture,  | 
no  attempt  has  been  made  to  map  them  on  a  textural  basis.     These 
areas  are  therefore  shown  as  Riverwash. 

The  recent  alluvial  fan  materials  occur  in  the  desert  in  the  western 
part  of  the  survey.  The  soil  derived  from  these  materials  is  corre- 
lated with  the  Carrizo  series. 

The  Carrizo  series  includes  types  with  gray  to  light  brownish  gray 
soils  and  subsoils  carrying  varying  quantities  of  fine  waterworn 
gravel.  In  the  subsoil  the  gravel  may  be  present  in  quantities  suffi- 
cient to  form  irregular  lenses  or  strata  of  some  thickness.  The  areas 
are  subject  to  overflow  at  infrequent  intervals,  and  much  of  the  land 
has  no  agricultural  value.  A  large  part  is  treeless,  but  in  the  imme- 
diate vicinity  of  the  channels  of  some  of  the  streams  there  is  a  scanty 
growth  of  mesquite  and  desert  shrubs. 

In  addition  to  the  soils  embraced  in  the  series  described  above  three 
types  of  a  miscellaneous,  nonagricultural  character  have  been  mapped.    , 
These  consist  of  Riverwash,  already  described,  Dnnesand,  and  Rough  } 
broken  land.     The  last  two  will  be  discussed  in  connection  with  the 
individual  types  in  succeeding  pages. 
58142°— 22 i 


26  FIELD   OPERATIONS   OF   THE  BUREAU   OF   SOILS,   1918. 

The   following  table  gives  the  name  and  the  actual  and  relative 
extent  of  the  various  soils  mapped  in  the  El  Centro  area: 

Areas  of  /afferent  soils. 


Soil. 


Holtvillesilty  clay 

Imperial  silty  clay 

Meloland  fine  sandy  loam, 
Holtville  silty  clay  loam. . 

Imperial  clay 

Imperial  silty  clay  loam. . 

Holtville  clay 

Rositas  very  fine  sand. . . . 

Rositas  fine  sand 

Superstition  fine  sand 

Rough  broken  land 

Dunesand 

Superstition  gravelly  sand 


Acres. 

Per 
cent. 

46,336 

14.4 

40,896 

12.7 

35,008 

10.9 

34,176 

10.6 

23, 744 

7.4 

18, 176 

5.6 

17, 216 

5.3 

17,024 

5.3 

11,584 

3.6 

11,264 

3.5 

9,664 

2.9 

8,960 

2.8 

8,384 

Soil. 


Carrizo  sand 

Holtville  very  fine  sandy  loam.. 

Rositas  sand 

Meloland  fine  sand 

Meloland  gravelly  sand 

Superstition  coarse  sand 

Tijeras  gravelly  fine  sandy  loam. 
Superstition  gravelly  coarse  sand . 

Riverwash 

Rositas  gravelly  fine  sand 

Rositas  very  fine  sandy  loam. . . 

Total 


Acres. 


6,912 
5,952 
4,544 
4,160 
4,096 
3,648 
3,392 
2,880 
1,856 
1,472 
1,216 


Per 
cent. 


2.1 
1.8 
1.4 
1.3 
1.3 
1.1 
1.0 
.9 
.6 
.5 
.4 


IMPERIAL   SILTY  CLAY  LOAM. 


The  surface  soil  of  the  Imperial  silty  clay  loam  consists  of  6  to  24 
inches  (and  very  rarely  72  inches)  of  a  pinkish-brown  to  chocolate- 
brown  or  purplish-brown  silty  clay  loam.  The  surface  soil  is  under- 
lain by  either  a  silty  clay  loam  or  a  clay  subsoil  extending  to  a  depth 
of  6  feet  or  more.  While  the  subsoil  may  consist  entirely  of  either 
of  these  materials,  uncommon^  it  is  composed  of  alternating  strata 
of  the  two  textures  and  thin  or  irregular  lenses  and  strata  of  fine 
sand  also  may  be  included.  The  subsoil  varies  in  color  from  a 
pinkish  gray  or  purplish  brown  to  a  dark  chocolate  brown,  and  is 
in  many  places  locally  mottled  with  reddish  colors  and  brown.  The 
texture  of  the  surface  soil  is  subject  to  considerable  variation.  In 
the  areas  of  lighter  soil  the  material  is  friable,  tills  easily,  and  seldom 
forms  a  hard  crust  on  the  surface  after  irrigation,  but  where  the  soil 
borders  the  silty  or  clay  types  of  the  series,  the  surface  is  often  very 
compact,  in  places  showing  a  tendency  toward  an  adobe  structure. 
The  subsoil  is  tough  and  compact  throughout,  offers  considerable 
resistance  to  the  movement  of  soil  moisture,  and  when  dry  has  a 
jointed  structure  or  breaks  into  small,  thin,  shaly  fragments.  The 
type  is  free  from  gravel. 

This  type  is  decidedly  calcareous,  both  in  the  soil  and  subsoil,  but 
the  lime  is  uniformly  distributed,  seldom  apparent  to  the  eye,  and 
as  yet  has  not  caused  cementation. 

The  boundaries  drawn  between  this  type  and  the  adjacent  soils 
are  arbitrary,  as  there  is  no  topographic  difference  on  which  to  base 
separation,  and  the  textures  of  the  soils  intergrade  and  change  very 
slowly. 


SOIL  SITEVEY  OF   THE   EL  CENTRO   AREA,   CALIFORNIA. 


27 


With  the  exception  of  a  few  shallow  depressions,  due  to  erosion 
by  the  flood  waters  from  the  Colorado  River,  the  surface  of  this  type 
is  very  uniform.  The  slope,  which  is  largely  to  the  north,  is  so 
gradual  that  the  land  is  apparently  level. 

This  type  originally  supported  a  scattered  growth  of  stunted 
mesquite  trees,  but  the  larger  part  of  the  native  vegetation,  which 
was  fairly  abundant,  consisted  of  desert  shrubs. 

The  soil  is  widely  scattered  throughout  the  survey  for  the  most 
part  in  irregular  areas  of  small  extent.  The  typical  areas  lie  in  the 
central  and  eastern  parts  of  the  survey.  In  these  internal  drainage 
is  rather  deficient,  owing  to  the  heavy  texture  and  compact  structure 
of  the  subsoil. 

The  larger  part  of  the  type  is  not,  at  the  present  time,  suffering 
from  the  presence  of  a  high  water  table,  but  in  small  areas  waste 
water,  apparently  coming  from  seepage  from  some  of  the  larger 
canals,  is  making  its  appearance,  resulting  in  an  unfavorably  moist 
soil  and  an  accumulation  of  alkali  salts. 

Practically  all  the  type  carries  more  than  0.2  per  cent  of  alkali, 
but  where  the  original  position  of  the  alkali  has  not  been  influenced 
by  seepage  conditions,  the  larger  part  of  it  is  found  in  the  heavier 
textured  subsoil.  Spotted  alkali  conditions  are  not  uncommon,  but 
affected  areas  are  seldom  of  more  than  one  or  two  acres  in  extent. 

Practically  all  of  this  type  is  under  cultivation  and  irrigation  at 
the  present  time.  Alfalfa,  cotton,  and  corn  form  the  principal  crops, 
and  a  considerable  acreage  is  devoted  to  some  of  the  extensively 
grown  truck  crops,  such  as  muskmelons,  lettuce,  and  tomatoes. 

The  following  table  gives  the  results  of  mechanical  analyses  of 
samples  of  the  soil  and  subsoil  of  this  type : 

Mechanical  analyses  of  Imperial  silty  clay  loam. 


Number. 

Description. 

Fine 
gravel. 

Coarse 
sand. 

Medium 
sand. 

Fine 
sand. 

Very  fine 
sand. 

Silt. 

Clay. 

575018 

Soil 

Per  cent. 

0.1 

.0 

Per  cent. 

0.1 

.1 

Per  cent. 
0.0 
.1 

Per  cent. 
1.1 
.7 

Per  cent. 
13.3 
24.9 

Per  cent. 
56.8 
47.7 

Per  cent. 

575019 

Subsoil 

26.6 

IMPERIAL    SILTY    CLAY. 


The  Imperial  silty  clay  consists  of  12  inches  to  3  feet  of  a  light 
purplish  brown  to  chocolate-brown  compact  silty  clay  underlain  to  a 
depth  of  6  feet  or  more  by  a  compact  tenacious  clay.  The  surface 
layer  of  soil,  one  or  two  inches  thick,  is  in  places  of  slightly  fluffy 
structure,  owing  to  the  presence  of  an  excessive  quantity  of  alkali 
salts,  but  otherwise  the  surface  soil  is  compact  throughout.     Within 


28  FIELD   OPERATIONS    OF    THE   BUREAU   OF   SOILS,   1918. 

tho  present  irrigated  parts  of  the  survey,  the  soil  and  subsoil  are  free 
from  gravel,  but  in  several  of  the  areas  of  soil  of  this  type  in  the 
western  and  northwestern  parts  of  the  area,  the  surface  has  a  heavy 
overwash  of  waterworn  gravel.  Such  areas  are  indicated  upon  the 
soil  map  by  gravel  symbols.  Because  of  their  small  extent,  a  few 
areas  of  the  clay  and  silty  clay  loam  types  of  the  series  have  been 
included  with  this  type.  They  can  ordinarily  be  distinguished  in  the 
field  by  the  texture  and  general  appearance  of  the  surface  material. 
The  silty  clay  grades  imperceptibly  into  the  other  members  of  the 
Imperial  series,  but  the  boundaries  between  it  and  the  lighter  tex- 
tured members  of  other  series  are  generally  well  defined. 

Both  the  surface  soil  and  subsoil  are  decidedly  calcareous.  Ap- 
parent accumulations  of  lime  do  not  occur  in  the  areas  under  the  pres- 
ent canals,  but  in  some  of  the  areas  on  the  desert  calcareous  material 
is  occasionally  concentrated  in  thin  partings  between  the  subsoil 
strata. 

This  type  is  widely  distributed  over  the  survey.  A  large  area  lies 
along  the  Mexican  boundary  line,  west  of  the  channel  of  New  River, 
and  an  area  of  considerable  size  occurs  in  and  south  of  the  town  of 
Imperial.  There  are  several  other  bodies  a  section  or  more  in  extent 
scattered  over  the  eastern  half  of  the  survey  and  areas  of  a  few  acres 
are  very  common. 

The  drainage  is  somewhat  deficient,  owing  to  the  compact  nature 
and  heavy  texture  of  the  subsoil.  So  far  there  is  no  widespread  dam- 
age resulting  from  irrigation,  and  the  only  areas  suffering  from  an 
excess  of  water  occur  where  seepage  from  some  of  the  canals  collects. 

Overirrigation  of  this  soil  may  eventually  give  rise  to  unfavor- 
able moisture  and  alkali  conditions,  but  owing  to  the  fact  that  per- 
colation and  capillary  movement  of  moisture  take  place  very  slowly 
and  it  is  almost  impossible  to  get  an  excess  of  irrigation  water  into  the 
soil  by  ordinary  irrigation,  and  to  the  fact  that  the  surface  evapora- 
tion is  exceedingly  high  in  this  region,  resulting  in  drying  out  the 
soil  between  spring  and  fall,  there  is  apparently  little  immediate 
danger  of  such  a  condition  arising. 

The  surface  of  larger  bodies  of  this  type,  while  apparently  level, 
have  a  sufficient  slope  to  carry  water  over  the  land  at  a  good  rate. 
Many  of  the  smaller  areas  have  this  same  character  of  surface,  but  a 
considerable  number  are  marked  by  small  hummocks  of  wind-blown 
materials  and  scattered  bodies  of  Dunesand.  On  the  desert,  in  the 
northwestern  part  of  the  survey,  the  surface  is  level  to  gently  rolling 
and  the  type  in  most  cases  occupies  a  slightly  lower  level  than  the 
surrounding  soil. 

Excepting  the  areas  lying  above  the  canals,  practically  all  this 
type  is  under  cultivation  at  the  present  time.     Over  most  of  it  the 


SOIL  SURVEY   OF   THE   EL   CENTRO   AREA,   CALIFORNIA. 


29 


farming  conditions  appear  to  be  satisfactory,  but  the  crop  yields  have 
been  low  on  a  few  of  the  areas,  owing  to  the  presence  of  an  excessive 
quantity  of  alkali. 

The  tilled  crops,  such  as  cotton  and  corn,  are  more  extensively 
grown  than  alfalfa,  as  the  subsoil  is  too  compact  for  the  best  results 
with  that  crop.  Muskmelons  and  other  truck  crops  are  important 
in  certain  localities.     (PL  III,  Fig.  1.) 

The  following  table  gives  the  results  of  mechanical  analyses  of 
samples  of  the  soil  and  subsoil  of  this  type : 

Mechanical  analyses  of  Imperial  silty  clay. 


Number. 

Description. 

Fine 
gravel. 

Coarse 
sand. 

Medium 
sand. 

Fine 
sand. 

Very  fine 
sand. 

Silt. 

Clay. 

575014.. 

Soil 

Per  cent. 

0.1 

.1 

Per  cent. 
0.3 

.7 

Per  cent. 
0.5 
1.1 

Per  cent. 
4.3 

6.8 

Per  cent. 
14.0 

5.7 

Per  cent. 
44.1 
50.9 

Per  cent. 
36.4 

575015 

Subsoil 

34.7 

IMPERIAL    CLAY. 


The  Imperial  clay  consists  of  6  feet  or  more  of  a  pinkish  light 
brown,  purplish-brown,  or  chocolate-brown  compact  clay.  The 
larger  part  of  the  type  is  free  from  gravel,  but  a  thin  overwash 
occurs  on  some  of  the  bodies  on  the  desert  west  of  the  Main  West 
Side  Canal.  In  this  region  also  there  are  occasional  hummocks  or 
thin  deposits  of  wind-blown  material  over  the  surface  of  the  clay. 

This  soil  is  ordinarily  compact  throughout  the  profile,  but  in  a  few 
places  alkali  salts  give  rise  to  a  fluffy  condition  in  the  immediate 
surface.  Where  the  texture  of  the  type  is  heaviest  the  surface  4  to 
6  inches  checks  like  adobe.  This  characteristic,  coupled  with  the 
presence  of  the  occasional  deposits  of  sand,  has  given  rise  to  a 
peculiar  condition,  the  wind  drifting  the  sand  into  the  cracks  and 
forming  irregular  nearly  vertical  seams  that  may  extend  to  a  depth 
of  several  inches. 

A  few  small  bodies  of  this  type  are  found  in  the  eastern  pait  of 
the  area,  but  its  principal  development  is  west  of  the  line  of  the 
Southern  Pacific  Railroad.  One  large  area  lying  west  of  the  town 
of  Imperial  extends  practically  the  entire  distance  across  T.  15  S., 
R.  13  E.,  and  across  New  River  into  R.  12  E.  Rather  extensive 
bodies  are  found  in  the  vicinity  of  the  town  of  Seeley  and  along 
the  Mexican  boundary  line  in  the  western  part  of  T.  17  S.,  R.  13  W. 
The  type  also  occurs  as  irregular  narrow  bodies  in  the  New  River 
gorge  or  wash,  between  the  areas  of  Riverwash  along  the  channel  of 
that  stream  and  the  bluffs. 
58142°— 22 5 


30  LD   OPERATIONS    OF   THE  BUREAU   OF   SOILS,   1918. 

The  surface  of  the  larger  pari  of  this  type  is  exceedingly  uniform 
an  J  is  apparently  level.  The  surface  irregularities  consist  of  the 
hummocks  of  wind-blown  material  already  mentioned,  which  occupy- 
but  local  areas,  and  the  winding  vertical  walled  ravines  or  channels 
eroded  by  the  action  of  the  flood  waters  from  the  Colorado  River 
before  New  River  wash  had  been  fully  developed.  These  erosions 
are  most  extensively  developed  west  of  Seeley,  where  they  render 
several  hundred  acres  of  land  untillable.  The  narrow  areas  in  the 
bottom  of  the  New  River  wash  usually  have  an  uneven  and  eroded 
surface  and  are  of  no  agricultural  value. 

This  soil  takes  up  water  very  slowly,  owing  to  its  unusually  heavy 
texture  and  compact  structure,  and  even  after  a  full  season's  irriga- 
tion the  subsoil  in  mamT  places  is  dry  below  a  depth  of  24  inches. 
There  is  but  little  seepage  from  the  canals  where  they  cross  this  soil, 
and  where  seepage  does  occur  the  water  is  retained  near  the  surface 
and  moves  but  a  short  distance  before  it  evaporates. 

The  average  content  of  alkali  in  the  soil  to  a  depth  of  6  feet  is 
usually  large,  field  tests  showing  more  than  3,000  parts  per  100,000, 
or  3  per  cent  of  salts,  in  many  places,  while  a  content  of  1  per  cent  is 
very  common.  This  alkali  may  be  uniformly  distributed  through- 
out the  profile,  but  it  is  more  commonly  the  case  that  the  surface  foot 
or  so  does  not  contain  enough  to  prevent  the  growth  of  plants  with- 
standing moderate  amounts. 

In  the  body  of  this  type  in  the  south  part  of  the  survey,  the  alkali 
content  averages  about  0.5  per  cent,  and  except  in  a  very  few  local 
spots  it  is  very  uniformly  distributed  throughout  the  soil  profile. 
In  some  fields  crops  show  a  spotted  condition,  but  on  the  whole  the 
growth  and  yields  of  cotton  and  corn  have  been  very  satisfactory. 
Around  Seeley  and  west  of  Imperial  the  quantity  of  alkali  in  the 
soil  is  seldom  below  1  per  cent,  and  the  general  condition  of  the 
crops  is  very  spotted.  In  many  cases  the  plants  make  a  growth  of 
but  a  few  inches  before  being  killed,  and  sometimes  the  seed  fails 
to  sprout.  In  the  smaller  areas  scattered  throughout  other  parts  of 
the  survey  the  alkali  content  varies  considerably,  but  in  most  of  these 
areas  the  amount  is  not  too  large  for  crop  growth. 

Cultivation  of  this  soil  is  difficult,  as  it  must  be  handled  when  in 
exactly  the  right  moisture  condition.  If  plowed  when  too  wet  it 
turns  up  in  large  plastic  lumps  that  are  almost  impossible  to  reduce 
to  a  good  tilth,  and  when  too  dry  it  breaks  up  into  large  clods  that 
can  not  be  satisfactorily  broken  down  until  after  further  irrigation. 
Where  the  quantity  of  alkali  has  not  prevented  the  cultivation  of  this 
soil  it  is  largely  utilized  for  cotton  and  corn.  Alfalfa  is  not  a  suc- 
cess, as  the  density  of  the  subsoil  prevents  the  proper  development 
of  the  root  system. 


SOIL  SURVEY  OF   THE   EL  CENTRO   AREA,    CALIFORNIA. 


31 


The  following  table  gives  the  results  of  mechanical  analyses  of 
samples  of  the  soil  and  subsoil  of  the  Imperial  clay  : 

Mechanical  analyses  of  Imperial  clay. 


Number. 

Description. 

Fine 
gravel. 

Coarse 
sand. 

Medium 
sand. 

Fine 
sand. 

Very  fine 
sand. 

Silt. 

Clay. 

575037 

Soil 

Per  cent. 
0.0 

Per  cent. 
0.7 
1.8 

Per  cent. 
2.0 
1.2 

Per  cent. 
14.7 
12.4 

Per  cent. 
6.3 
8.9 

Per  cent. 
32.5 
34.0 

Per  cent. 
44. 2 

575D38 

Subsoil......              .0 

41.7 

HOLTVILLE  VERY  FINE   SANDY  LOAM. 


The  surface  soil  of  the  Holtville  very  fine  sandy  loam  is  a  light- 
brown  or  pinkish  or  light  purplish  brown  slightly  micaceous  very 
fine  sandy  loam.  The  surface  material  of  this  type  frequently  in- 
cludes one  or  more  strata,  each  1  to  3  inches  thick,  of  compact  slightly 
heavier  textured  materials,  and  there  is  a  succession  of  similar  strata 
at  intervals  of  about  36  inches  to  an  indefinite  depth.  The  structure 
of  the  subsoil  is  slightly  compact.  Surface  and  subsoil  are  both  dis- 
tinctly calcareous.  The  texture  and  structure  are  very  uniform 
throughout  the  main  body  of  the  soil,  except  where  it  merges  into  the 
surrounding  soils,  and  where  small  amounts  of  wind-blown  sand  have 
accumulated. 

This  type  occurs  as  three  areas  south  of  Holtville.  The  larger 
areas  extend  about  1|  miles  south  of  Holtville  southward  on  the  west 
side  of  the  Alamo  River  nearly  to  the  Mexican  boundary.  The  smaller 
body  lies  in  the  southern  part  of  T.  16  S.,  R.  16  E. 

The  usual  position  of  the  type  is  somewhat  above  the  general  eleva- 
tion of  the  surrounding  soils,  and  the  areas  appearing  as  low  sandy 
elevations  are  distinguishable  for  some  distance.  An  old  drainage 
depression  from  20  to  30  feet  in  depth  and  extending  from  the  Alamo 
River  in  a  northwesterly  direction  across  the  northern  part  of  T.  16 
S.,  R.  15  E.,  forms  the  most  prominent  surface  irregularity  within 
the  type.  Wind  erosion  has  removed  considerable  areas  of  this  soil, 
leaving  a  part  of  the  type  with  a  miniature  badland  topography,  but 
much  of  the  surface  is  uniform  or  but  slightly  rolling. 

The  drainage  of  the  soil  is  good,  but  not  excessive,  owing  to  the  very 
fine  texture  of  the  subsoil  and  its  slight  compactness. 

A  large  part  of  this  soil  lies  slightly  above  any  available  gravity 
supply  of  irrigation  water,  and  a  part  of  it  is  being  irrigated  by 
pumping  from  near-by  canals.  Where  the  type  is  under  cultivation 
alfalfa  occupies  the  larger  acreage,  the  grains  ranking  second.  Cotton 
and  corn  are  seldom  grown,  and  its  best  adaptation  will  probably  be 
found  in  the  crops  which  are  now  largely  grown  upon  it. 


32 


FIELD  OPERATIONS   OE   TUB   BUREAU   OF   SOILS,  1918. 


Tin    following  table  gives  the  results  of  mechanical  analysis  of  a 
sample  of  the  soil  of  the  Holtville  very  fine  sandy  loam: 

Mechanical  analysis  of  Holtville  very  fine  sandy  loam. 


Number. 

Description. 

Fine 

gravel. 

sand. 

Medium 
sand. 

Pine 

sand. 

Very  fine 
sand. 

Silt. 

Clay. 

676048 

Soil 

Per  cent. 
0.0 

Per  cent. 
0.0 

Per  cent. 
0.1 

Per  cent. 
3.4 

Per  cent. 
49.2 

Per  cent. 
40.2 

Per  cent. 
6.9 

HOLTVILLE    S1LTY    CLAY    LOAM. 

The  surface  soil  of  the  Holtville  silty  clay  loam  consists  of  6  tO' 
30  inches  of  a  light  purplish  brown  to  a  chocolate-brown  silty  clay 
loam,  underlain  by  either  a  fine  sand  or  a  fine  sandy  loam  subsoil 
extending  to  a  depth  of  6  feet  or  more.  The  subsoil  may  be  uniform 
in  texture,  but  more  commonly  consists  of  alternating  strata  of  fine 
sand  and  fine  sand.37  loam.  A  layer  of  compact  clay  is  often  en- 
countered at  the  depth  of  about  6  feet,  and  this  may  be  several  feet 
in  thickness  or  be  only  a  thin  parting  in  the  lighter  textured  mate- 
rial. As  with  the  silty  clay  loam  of  the  Imperial  series,  the  surface 
soil  of  this  type  varies  considerably  in  texture,  the  lighter  varia- 
tions being  friable,  and  often  difficult  to  distinguish  from  the  heavier 
variations  of  some  of  the  fine  sandy  loam  types.  On  the  other  hand. 
the  soil  in  some  places  approximates  a  silty  clay  loam  in  texture. 
This  type  is  free  from  gravel. 

Both  soil  and  subsoil  are  calcareous,  but  no  cementing  of  the  mate- 
rial has  as  yet  taken  place,  the  lime  being  uniformly  distributed 
through  the  soil  mass. 

Aside  from  the  presence  of  small  deposits  of  wind-blown  mate- 
rials lodged  around  the  desert  shrubs,  and  an  occasional  isolated 
sand  dune,  the  surface  of  this  type  is  very  uniform.  The  only  promi- 
nent surface  irregularity  within  it  is  the  deep  wash  of  New  River, 
which  traverses  one  of  the  larger  bodies  of  this  soil  for  a  distance 
of  several  miles. 

The  most  prominent  areas  are  situated  in  the  southern  and  western 
central  parts  of  the  survey,  extending  northwest  from  Calexico 
along  the  channel  of  New  River.  These  are  the  most  prominent 
areas  west  of  the  line  of  the  Southern  Pacific  Railroad;  east  of  that 
line  the  type  is  confined  to  widely  scattered  and  rather  small  areas. 

The  drainage  is  generally  good,  but  in  a  few  places,  along  some  of 
the  larger  canals,  seepage  has  apparently  developed  unfavorable 
moisture  conditions.  In  the  larger  body  of  this  type  along  New 
River,  the  deep  gorge  of  this  stream  affords  an  excellent  drainage 
outlet,  and  there  is  but  little,  if  any,  danger  that  the  soil  here  will 
ever  become  waterlogged. 


SOIL   SURVEY   OF   THE  EL   CENTRO   AREA,   CALIFORNIA. 


33 


Practically  all  of  the  surface  soil  of  this  type  contains  small  quan- 
tities of  alkali,  and  locally  amounts  sufficient  to  injure  crops.  The 
subsoil  in  most  of  the  type  carries  very  little  alkali,  but  where 
heavier  subsoil  strata  are  present  they  usually  contain  more  than 
0.2  per  cent.  Aside  from  areas  where  the  alkali  has  been  concen- 
trated by  seepage  waters,  the  only  noticeable  occurrences  are  small 
spots  or  areas  around  the  margins  of  the  type,  adjacent  to  soils  more 
strongly  impregnated. 

Nearly  all  of  this  type  is  under  cultivation,  largely  to  alfalfa  and 
cotton.  In  the  extreme  eastern  part  of  the  area  a  few  small  areas 
have  become  too  wet,  apparently  through  seepage,  for  cultivation, 
and  have  been  abandoned. 

The  following  table  gives  the  results  of  mechanical  analyses  of 
samples  of  the  soil  and  subsoil  of  the  Holtville  silty  clay  loam : 

Mechanical  analyses  of  Holtville  silty  clay  loam. 


Number. 

Description. 

Fine 
gravel. 

Coarse 
sand. 

Medium 
sand. 

Fine 
sand. 

Very  fine 
sand. 

Silt. 

Clay. 

575003... 

Soil 

Per  cent. 
0.1 
.0 

Per  cent. 

0.1 

.0 

Per  cent. 
0.0 
.1 

Per  cent. 
0.4 
1.3 

Per  cent. 
6.9 
44.8 

Per  cent. 
67.7 

46.6 

Per  cent. 
24.8 

575004 

6.9 

HOLTVILLE    SILTY   CLAY. 


The  Holtville  silty  clay  consists  of  12  to  24  inches  of  a  light  pinkish 
or  purplish  brown  to  a  chocolate-brown  compact  silty  clay,  under- 
lain by  fine  sand  or  fine  sandy  loam  carrying  occasional  thin  strata 
of  heavier  materials.  The  surface  soil  is  very  compact,  much  of  it 
closely  approaching  a  clay  in  texture,  and  small  bodies  of  the  clay 
type  of  the  series  too  small  to  be  shown  upon  the  soil  map  are  in- 
cluded.    Both  the  soil  and  subsoil  are  strongly  calcareous. 

This  type  is  distributed  throughout  the  survey.  The  most  im- 
portant areas,  lying  south  of  El  Centro,  average  some  6  or  7  miles 
in  length  and  somewhat  more  than  1  mile  in  width.  Other  areas 
almost  as  large  occur  north  and  east  of  Holtville.  In  the  vicinity 
of  Imperial  there  are  a  large  number  of  areas  each  containing  a 
square  mile  or  more. 

Where  the  heavy  surface  material  of  this  type  is  of  considerable 
depth,  the  drainage  is  slightly  deficient,  as  it  is  sufficiently  compact 
to  prevent  the  downward  movement  of  the  water.  Where  the  sur- 
face soil  is  shallow  the  drainage  is  good.  In  a  body  of  this  soil 
southeast  of  Holtville  in  T.  16  S.,  R.  16  E.,  some  unfavorable 
moisture  conditions  have  resulted  through  seepage,  but  aside  from 
this  no  ill  effects  have  followed  the  irrigation  of  this  type. 


34  FIELD  OPERATIONS   OP   T11K  BUREAU    OF   SOILS,   1918. 

Practically  all  the  Iloltville  silty  clay  carries  more  than  0.2  of  1 
per  rent  of  alkali,  with  most  of  it  below  a  depth  of  18  inches.  Ex- 
ception must  hi-  made  of  one  area  about  4  miles  northeast  of  Holt- 
ville.  where  the  alkali  content  is  over  1  per  cent,  with  a  large  part 
of  this  in  the  immediate  surface  soil.  The  alkali  in  this  area  was 
present  before  there  was  any  irrigation  in  the  valley.  Attempts 
have  been  made  to  place  this  land  under  cultivation,  but  it  is  largely 
unutilized  at  the  present  time. 

The  surface  of  the  larger  part  of  this  type  is  very  uniform.  In 
the  western  part  of  the  survey,  where  this  soil  is  associated  with  soils 
of  the  Superstition  series,  the  surface  in  places  is  marked  by  accu- 
mulations of  wind-blown  sands. 

Some  of  the  areas  of  this  type  lie  above  the  present  canal  systems 
and  are  not  irrigated.  Below  the  canals  nearly  all  of  it  excepting 
the  area,  heavily  impregnated  with  alkali,  northeast  of  Holtville,  is 
under  cultivation.  Cotton,  corn,  barley,  and  alfalfa  are  all  grown, 
the  latter  occupying  a  relatively  small  acreage.  It  is  well  adapted 
to  the  first  three  crops.  Muskmelons  and  lettuce  are  grown  to  some 
extent,  but  the  total  acreage  of  truck  crops  is  small. 

HOLTVILLE   CLAY. 

The  Holtville  clay  consists  of  12  to  36  inches  of  a  light  pinkish  or 
purplish  brown  to  chocolate-brown  compact  heavy  textured  clay, 
underlain  by  slightly  lighter  colored  compact  fine  sandy  loam  or  silt 
loam,  fine  sand  occurring  in  places.  The  line  between  the  surface 
soil  and  subsoil  is  sharp,  and  when  the  subsoil  is  made  up  of  alter- 
nating strata  the  division  between  each  also  is  very  definite.  The 
surface  soil  is  normally  compact,  except  where  the  surface  layer, 
1  or  2  inches  thick,  is  loose  and  fluffy  because  of  the  presence  of  an 
excess  of  alkali  salts.  Both  surface  and  subsoil  contain  much  lime, 
which  is  quite  uniformly  distributed. 

A  few  small  areas  of  this  type  are  found  in  the  eastern  part  of  the 
survey,  but  its  principal  development  is  in  the  west-central  part,  ad- 
jacent to  the  channel  of  New  River,  from  about  4  miles  south  of 
Seeley  northward  nearly  to  the  northern  boundary. 

Much  of  the  original  surface  of  this  type  was  smooth  and  level, 
about  the  only  irregularities  consisting  of  the  accumulations  of  wind- 
blown materials  about  the  desert  shrubs.  Flood  waters  from  the 
Colorado  River  have  eroded  deep  vertical-walled  washes  in  some 
areas.  Several  hundred  acres  have  thus  been  rendered  unfit  for  cul- 
tivation. 

Owing  to  the  compactness  of  the  surface  soil,  the  internal  move- 
ment of  moisture  is  slow,  and  in  many  places  the  material  is  not  wet 
below  2  feet,  even  following  a  season's  irrigation. 


SOIL  SURVEY   OF   THE  EL  CENTEO   AREA,   CALIFORNIA.  35 

There  are  some  small  areas  of  this  soil  that  contain  less  than  0.2 
per  cent  alkali,  but  the  most  of  it  carries  more  than  that  amount, 
and  a  considerable  part  more  than  1  per  cent.  Field  tests  show  that 
the  larger  part  of  the  alkali  occurs  below  a  depth  of  18  inches. 

This  type  is  one  of  the  difficult  soils  in  the  area  to  cultivate.  Un- 
less handled  exactly  at  the  right  time,  with  respect  to  the  moisture 
condition,  a  rough,  cloddy  surface  results,  and  once  in  this  condition 
it  is  extremely  difficult  to  put  a  field  in  good  tilth. 

A  large  part  of  the  Holtville  clay  is  under  cultivation.  It  is  de- 
voted largely  to  the  production  of  cotton  and  corn.  Alfalfa  is  seldom 
grown  on  this  heavy  soil.  Some  of  the  land  has  been  abandoned  be- 
cause of  the  unfavorable  alkali  conditions. 

TIJERAS   GRAVELLY  FINE   SANDY   LOAM. 

The  surface  soil  of  the  Tijeras  gravelly  fine  sandy  loam  where 
typically  developed  consists  of  3  feet  or  more  of  pale-red,  brownish- 
red,  or  reddish-brown  compact  fine  sandy  loam,  carrying  a  large  pro- 
portion of  waterworn  gravel.  As  mapped  in  this  survey,  however, 
considerable  areas  have  a  brown  or  grayish-brown  color  approaching 
that  of  the  Superstition  series,  the  two  series  where  adjoining  pass- 
ing gradually  one  into  the  other  and  making  it  necessary  to  compro- 
mise in  placing  the  boundaries. 

The  subsoil  is  normally  grayish-brown  or  light  grayish  red  to 
reddish-brown,  compact,  and  calcareous  clay;  but  in  some  of  the 
included  nontypical  areas  it  consists  of  a  coarse,  porous  sandy  ma- 
terial extending  to  6  feet  or  more. 

The  deeper  subsoil  and  substratum  is  composed  of  compacted  and 
stratified  clay,  the  layers  in  many  places  separated  by  strata  of  soft 
concretionary  sandstones.  Both  the  soil  and  subsoil  are  calcareous. 
Concentrations  of  lime  appear  in  the  soil  within  a  few  inches  of 
the  surface,  either  as  thin  sheets  or  as  concretions,  and  the  material 
is  in  many  places  cemented  into  a  soft  hardpan.  The  heavier  subsoil 
is  not  only  highly  calcareous,  *  but  also  carries  small  amounts  of 
gypsum  and  alkali  incrustations  or  crystals  between  the  clay  strata. 

This  type  is  confined  to  the  southwestern  part  of  the  area,  where 
it  occurs  largely  on  the  top  of  an  irregular  mesa.  A  few  areas  also 
occur  in  the  same  general  region  on  the  floor  of  the  desert. 

The  soil  on  the  mesa  has  a  uniform  or  gently  rolling  to  steep  and 
eroded  surface,  the  latter  on  the  mesa  slopes.  The  lower  lying  areas 
are  slightly  rolling,  and,  as  a  rule,  lie  slightly  higher  than  the  sur- 
rounding soils. 

The  lower  bodies  of  this  type  probably  will  have  some  agricultural 
value  when  irrigation  water  is  made  available,  for  this  part  of  the 
area,  but  the  larger  mesa  area  has  no  present  or  prospective  value>  as 
it  lies  too  high  for  irrigation. 


36 


FIELD  OPERATIONS   OF   THE   BUREAU    OF   SOILS,  1918. 


The  following  table  gives  the  results  of  mechanical  analysis  of  a 
sample  o['  the  soil  of  the  Tijeras  gravelly  fine  sandy  loam: 

Mechanical  analysis  of  Tijeras  gravelly  fine  sandy  loam. 


Number. 

Description. 

Fine 
gravel. 

Coarse 
sand. 

Medium 
sand. 

Fine 
sand. 

Very  fine 
sand. 

Silt. 

Clay. 

Soil 

Per  cent. 
2.1 

Per  cent. 
7.7 

Per  cent. 
4.3 

Per  cent. 
28.6 

Per  cent . 
11.8 

Per  cent. 
20.7 

Per  cent. 
18.9 



SUPERSTITION  GRAVELLY  COARSE  SAND. 


Both  the  soil  and  subsoil  of  the  Superstition  gravelly  coarse  sand 
consists  of  a  mixture  of  light-gray  or  light  brownish  gray  very  coarse 
sand  and  fine  waterworn  gravel.  The  larger  part  of  the  gravel  is 
formed  of  quartz  particles  about  the  size  of  rice  grains,  but  locally, 
especially  along  the  beach  line  in  the  eastern  part  of  the  area,  there 
is  a  noticeable  admixture  of  coarser,  dark-colored  gravel. 

Both  surface  soil  and  subsoil  are  calcareous.  Along  the  line  of 
the  beach  accumulations  of  lime  are  not  visible,  but  in  the  apparently 
older  areas  in  the  extreme  western  part  of  the  area  concentrations 
occur  in  the  form  of  large  irregular  concretions,  in  both  soil  and 
subsoil.  In  a  number  of  places  the  removal  of  some  of  the  surface 
soil  by  winds  has  left  these  concretions  protruding  a  few  inches  above 
the  surface. 

The  larger  part  of  this  type  occurs  as  nearly  continuous  low  ridges 
extending  across  the  area  from  north  to  south  on  both  sides  of  the 
valley.  These  ridges  mark  the  line  of  the  beach  of  the  last  body  of 
water  and  represent  the  coarser  material  thrown  up  by  the  waves 
along  the  shore.  The  more  elevated  bodies  in  the  extreme  western 
part  of  the  area  represent  either  an  old  beach  line,  now  nearly  ob- 
literated, or  else  bars  formed  in  shallow  water.  In  general,  the  sur- 
face of  the  type  is  rolling. 

The  type  Superstition  gravelly  coarse  sand  has  no  agricultural 
value,  both  its  coarse  texture  and  uneven  topography  being  unfavor- 
able. 


SUPERSTITION   COARSE   SAND. 


The  surface  soil  of  the  Superstition  coarse  sand  consists  of  6  to 
12  inches  of  a  light-gray  to  light  brownish  gray  coarse  sand,  in  places 
carrying  a  considerable  admixture  of  fine  gravel  occurring  mainly  on 
the  surface.  The  subsoil  is  similar  to  the  surface  soil  in  texture  and 
structure,  but  is  normally  slightly  lighter  in  color.  Stratification 
occurs  in  both  soil  and  subsoil,  but  the  various  layers  ordinarily  are 
not  sharply  separated.  The  soil  is  uniform  in  texture  and  structure, 
the  only  noticeable  variation  in  the  surface  material  consisting  of 


SOIL  SURVEY  OF  THE  EL   CENTRO  AREA,   CALIFORNIA.  37 

accumulations  of  wind-blown  materials,  either  around  shrubs  or  in 
larger  isolated  dunes. 

The  type  occupies  a  level  to  gently  rolling  surfaced  mesa  in  the 
extreme  southwestern  part  of  the  area. 

None  of  this  type  is  under  irrigation,  and  owing  to  its  elevation  it 
probably  will  be  many  years  before  water  will  be  available.  The 
surface  soil  and  subsoil  are  very  porous  and  low  in  organic  matter, 
and  a  large  amount  of  water  would  be  required  for  any  crop  that 
might  be  grown.  Alfalfa  would  probably  be  found  better  adapted 
to  this  soil  than  would  the  shallower  rooted  crops. 

SUPERSTITION    GRAVELLY    SAND. 

The  surface  soil  of  the  Superstition  gravelly  sand  consists  of  6  to 
18  inches  of  a  light  grayish  brown  or  light  brownish  gray  sand,  which 
contains  varying  quantities  of  fine  to  medium,  waterworn  gravel. 
The  surface  soil  always  carries  a  rather  large  proportion  of  gravel, 
and  there  is  usually  an  appreciable  amount  of '  it  in  the  subsoil 
though  locally  there  may  be  none.  The  color  of  the  subsoil  is  similar 
to  that  of  the  surface  soil.  The  texture  and  structure  are  extremely 
variable,  ranging  from  pure  gravel  to  rather  heavy  loam.  Over 
the  larger  part,  however,  it  is  a  light-textured  sandy  loam  or  fine 
sandy  loam.  In  most  places  it  is  stratified,  but  very  irregularly, 
strata  of  any  given  material  ordinarily  extending  but  short  distances 
and  varying  greatly  in  thickness. 

Both  the  surface  soil  and  subsoil  are  high  in  lime.  The  former 
seldom  carries  any  visible  concentrations,  but  the  subsoil  normally 
contains  thin  irregular  deposits  of  calcareous  material  between  the 
different  strata  or  in  larger  concretionary  masses,  irregularly  dis- 
tributed. In  many  places  the  coarser  gravel  has  a  thin  whitish  coat- 
ing of  lime. 

Variations  from  the  above  description  occur  along  the  margins  of 
the  various  areas  either  as  the  result  of  a  local  reworking  or  of 
zones  of  gradation  between  this  and  adjacent  types.  The  most 
notable  variation  of  the  latter  sort  is  along  the  contact  of  bodies 
of  this  soil  and  the  Hough  broken  land  in  the  northern  part  of 
T.  16  S.,  R.  11  E.  The  Rough  broken  land  here  consists  of  a  narrow 
eroded  belt  between  this  type  and  the  lower  bodies  of  recent  alluvial 
soils ;  and,  in  such  locations  heavy-textured  stratified  materials,  such 
as  occur  in  the  Imperial  series,  are  locally  present  in  the  subsoil. 

The  larger  part  of  this  type  lies  in  the  western  part  of  T.  16  S., 
R.  11  E.,  west  of  the  old  beach  line.  A  few  smaller  areas  occur 
below  that  line,  and  also  in  the  eastern  part  of  the  area  just  below 
the  old  beach  line  in  T.  15  S.,  R.  16  E. 

In  a  few  localities  there  is  no  distinct  line  of  demarcation  between 
this  type  and  the  adjacent  soils.    It  usually  occurs,  however,  as  level 


88 


FIELD  OPERATIONS   OF   Till:   BUREAU    OF   SOILS,   1918. 


to  gently  rolling  areas,  slightly  above  the  recently  formed  soils,  from 
which  it  is  separated  either  by  narrow  belts  of  Rough  broken  land  or 
by  nearly  vertical  slopes  or  terrain's  a  few  feel  high,  and  is  thus 
easily  distinguishable.    The  drainage  is  excessive. 

The  soil  is.  as  a  whole,  free  from  alkali,  the  latter,  where  present, 
Occurring  in  the  deeper  subsoil  only  within  a  very  narrow  area  along 
the  boundary  between  this  type  and  bodies  of  the  heavier  soils  of 
the  Imperial  series. 

Very  little  of  this  type  is  under  cultivation  at  the  present  time, 
as  only  the  narrow  body  in  the  northeastern  corner  of  the  area  is 
below  the  present  canal  system.  The  native  vegetation  consists  of  a 
scattered  growth  of  creosote  bush  and  other  low  desert  shrubs.  The 
topography  is  favorable  to  irrigation  and  cultivation  and  the  type 
should  be  well  adapted  to  the  growing  of  alfalfa  when  water  is 
made  available. 

The  following  table  gives  the  results  of  mechanical  analyses  of 
samples  of  the  soil  and  subsoil  of  the  Superstition  gravelly  sand: 

Mechanical  analyses  of  Superstition  gravelly  sand. 


Number. 

Description. 

Fine 

gravel. 

Coarse 

sand. 

Medium 
sand. 

Fine 
sand. 

Very  fine 
sand. 

Silt. 

Clay. 

575026 

Soil 

Per  cent. 
5.G 
6.1 

Per  cent. 
17.0 
11.1 

Per  cent. 
10.1 
6.0 

Per  cent. 
3s.  A 
50.7 

Per  cent. 
11.6 
15.7 

Per  cent. 
11.1 

6.7 

Per  cent. 
6.3 

575027 

Subsoil 

3.6 

SUPERSTITION  FINE  SAND. 


The  surface  soil  of  the  Superstition  fine  sand  consists  of  6  to  18 
inches  of  light  brownish  gray  fine  sand,  containing  a  relatively 
large  proportion  of  medium  and  coarse  sand  material.  The  soil 
passes  gradually  into  the  subsoil,  which  is  a  light-gray  or  light 
brownish  gray  light-textured  compact  fine  sandy  loam,  carrying  in 
places  considerable  quantities  of  fine  waterworn  gravel.  In  places 
it  may  consist  of  varying  strata  of  gravel,  coarse  sand,  fine  sand,  and 
sandy  loam.  Stratification  occurs  also  in  the  surface  soil.  The  char- 
acter of  the  immediate  surface  material  in  many  places  has  been 
changed  by  the  action  of  the  wind,  either  through  the  removal  of 
the  lighter  textured  materials,  or  by  the  development  of  hummocks 
and  isolated  bodies  of  sand.  In  the  east  central  part  of  T.  15  S.,  E. 
HE.,  one  area  of  this  type  carries  a  large  proportion  of  waterworn 
gravel  on  the  surface,  and  the  texture  of  the  surface  soil  approxi- 
mates a  fine  sandy  loam.  The  areas  of  this  t}-pe  in  T.  15  S.,  E.  1C  E., 
east  of  the  East  Side  High  Line  Canal  are  also  somewhat  heavier  in 
texture  than  typical.  Accumulations  of  surface  gravel  are  indicated 
on  the  soil  map  by  means  of  s37mbols. 


SOIL   STOVEY   OF   THE   EL   OENTRO   AREA,   CALIFORNIA.  39 

The  surface  soil  is  slightly  calcareous,  but  is  not  cemented.  The 
subsoil  is  high  in  lime,  compact,  carries  thin  irregular  seams  of  cal- 
careous material  throughout  the  deeper  part,  and  contains  lime- 
coated  gravel.  Locally  the  subsoil  is  firmly  cemented,  but  softens 
soon  after  the  application  of  water. 

This  type  is  quite  clearly  separated  from  the  old  beach-line  soil 
(Superstition  gravelly  coarse  sand)  by  a  distinct  difference  in  eleva- 
tion, but  the  line  of  separation  between  the  Superstition  fine  sand 
and  the  other  types  of  soil  is  very  indistinct,  and  many  of  the  bound- 
aries are  arbitrary. 

This  type  is  most  extensively  developed  in  the  western  part  of  the 
area,  largely  between  the  old  beach  line  and  the  Main  West  Side 
Canal.  Only  one  small  area  lies  east  of  the  canal,  and  only  a  few 
areas  above  the  old  beach. 

The  surface  is  level  to  gently  rolling,  and  the  only  noticeable 
irregularities  consisting  of  isolated  sand  dunes  and  accumulations 
of  wind-blown  sand  around  the  bases  of  shrubs. 

The  type  is  well  drained  and  free  from  alkali,  except  in  the  small 
area  east  of  the  canal,  where  seepage  has  caused  a  high  water  table. 

None  of  the  type  is  under  cultivation  at  the  present  time.  The 
area  under  the  canal  formerly  was  in  alfalfa,  but  the  unfavorable 
moisture  and  alkali  conditions  have  caused  it  to  be  abandoned.  When 
water  is  available  for  this  type,  it  will  probably  be  found  better 
adapted  to  alfalfa  than  to  the  tilled  crops  usually  grown  in  the 
valley. 

MELOLAND   GRAVELLY    SAND. 

The  surface  soil  of  the  Meloland  gravelly  sand  consists  of  6  to  36 
inches  of  a  light  grayish  brown  to  light-brown,  or  slightly  purplish 
brown  slightly  sticky  or  loamy  sand,  containing  a  considerable  quan- 
tity of  small  waterworn  gravel.  The  subsoil  is  brown  to  purplish  or 
chocolate  brown  in  color  and  consists  of  a  compact  silty  clay  loam, 
silty  clajr,  or  a  clay  extending  to  a  depth  of  6  feet  or  more,  though 
thin  lenses  or  layers  of  lighter  textured  sediments  may  be  included. 
The  surface  material  has  been  reworked  to  a  varying  extent  by  the 
wind,  resulting  either  in  the  removal  of  the  finer  material  and  a  sur- 
face concentration  of  gravel  or  in  the  development  of  small  dunes. 

The  surface  of  the  Meloland  gravelly  sand  is  gently  rolling  to 
hummocky.  The  drainage  is  slightly  deficient.  The  soil  is  ordi- 
narily free  from  alkali,  but  the  subsoil  in  most  places  carries  consid- 
erable quantities. 

This  type  occurs  mainly  in  the  northwestern  part  of  the  area.  It 
is  entirely  above  the  present  canal.  Parts  of  it  have  been  leveled  and 
checked,  but  none  of  it  is  under  cultivation.  It  will  probably  be 
found  well  adapted  to  alfalfa  and  the  various  tilled  crops,  the  former 


40 


FIELD  OPERATIONS   OF    I  in:    l'-UREAU  OF  SOILS,  1018. 


particularly  in  those  districts  where  the  heavier  subsoil  lies  at  a  con- 
siderable  depth. 
The  Following  table  gives  the  results  of  mechanical  analyses  of 

samples  of  the  soil,  subsoil,  and  lower  subsoil  of  the  Meloland  grav- 
elly sand : 

Mechanical  analyses  of  Meloland  gravelly  sand. 


Number. 

Descri]>ti.<n. 

Fine 
gravel. 

Coarse 
sand. 

Medium 
saud. 

Fine 
sand. 

Very  fine 

sand. 

Silt. 

Clay. 

575032 

Soil 

Per  cent. 
5.1 

2.7 

B   1 

Per  cent. 
14.4 
4.2 
14.0 

Per  cent. 

7.4 
2.3 
4.8 

Per  cent. 

45.  9 
14.9 
24.2 

P(  r  a  fit . 
16.9 

9.4 
7.9 

Per  cent. 

0.9 

30.6 

18.8 

Ptr  a  nt. 
9.4 

575033 

Subsoil 

35.8 

575034 

Lower  subsoil... 

22.0 

MELOLAND    FINE    SAND. 


The  Meloland  fine  sand  consists  of  a  loose  incoherent  yellowish- 
brown  or  light  grayish  brown  fine  sand  extending  to  a  depth  of  12 
to  30  inches,  underlain  by  compact  purplish  or  chocolate-brown  or 
brown  silty  clay  loam,  silty  clay,  or  clay. 

The  subsoil  may  extend  to  a  depth  of  6  feet  without  change,  or 
may  consist  of  interstratified  beds  including  locally  material  of 
lighter  texture.  In  typical  areas  the  fine  sand  surface  soil  extends 
to  the  depths  stated  above,  but  owing  to  the  action  of  the  wind  has 
heaped  the  surface  soil  into  dunes  from  6  to  10  feet  in  height,  expos- 
ing the  heavy  subsoil  materials  in  the  intervening  depressions. 

Typical  areas  of  this  type  are  developed  only  in  T.  15  S.,  R.  12 
E.  The  duny  areas,  which  contain  but  a  few  acres  each,  occur  rather 
widely  distributed  throughout  Ts.  15  and  16  S.,  E.  12  E. 

The  subdrainage  of  this  type  is  slightly  deficient  and  the  subsoil 
carries  some  alkali.  The  surface  soil  is  free  from  excessive  alkali  ac- 
cumulations. 

Only  a  few  acres  of  Meloland  fine  sand  have  so  far  been  leveled  for 
irrigation  and  none  of  it  is  under  cultivation.  Water  is  available 
for  but  a  small  part  of  the  type,  as  it  lies  largely  above  the  present 
canals.  Under  irrigation  the  areas,  where  the  heavier  subsoils  are  at 
a  considerable  depth,  will  be  suited  to  the  growing  of  alfalfa,  and 
those  of  more  shallow  soil  to  grains  or  cotton. 

The  following  table  gives  the  results  of  mechanical  analyses  of 
samples  of  the  soil  and  subsoil  of  the  Meloland  fine  sand : 

Mechanical  analyses  of  Meloland  fine  sand. 


Number. 

Description. 

Fine 
gravel. 

Coarse 
sand. 

Medium 
sand. 

Fine 
sand. 

Very  fine 
sand. 

Silt. 

Clay. 

575039 

Soil 

Per  cent. 

0.0 

.0 

Per  cent. 
1.6 
1.7 

Per  cent. 
8.7 
2.2 

Per  cent. 

69.3 

7.9 

Per  cent. 
10.6 
5.6 

Per  cent. 
3.6 
12.8 

Per  cent. 
6.2 

575040 

Subsoil 

69.9 

SOIL  SURVEY   OF   THE   EL   CENTRO   AREA,   CALIFORNIA.  41 


MELOLAND    FINE    SANDY   LOAM. 


The  Meloland  fine  sandy  loam  is  typically  a  light-brown  to  a  light 
pinkish  or  purplish  brown  friable  fine  sandy  loam,  from  12  to  36 
inches  deep,  underlain  by  a  silty  clay  loam,  silty  clay,  or  clay,  extend- 
ing to  6  feet  or  more.  The  predominating  texture  of  the  subsoil  is 
silty  clay  loam  or  silty  clay,  but  any  of  the  textures  mentioned  may 
occur  in  well-defined  strata,  and  these  irregular  pockets  or  layers  of 
lighter  textured  sediments  may  be  included  locally.  The  heavier 
strata  are  compact.  The  color  of  the  subsoil  is  predominantly  a 
brown,  but  may  be  brown  mottled  with  either  reddish  or  grayish 
stains. 

Several  areas  of  this  soil,  particularly  west  of  Holtville,  approach 
a  loam  in  texture,  and  to  the  south  of  Holtville  several  areas  resemble 
the  very  fine  sand  of  the  Rositas  series  in  that  the  subsoil  occasionally 
carries  thin  strata  or  seams  of  lighter  textured  materials. 

Both  soil  and  subsoil  of  the  Meloland  fine  sandy  loam  are  calcareous, 
but  no  cementation  has  taken  place  and  no  concretions  or  other  ac- 
cumulations of  lime  have  developed. 

Meloland  fine  sandy  loam  is  widely  distributed  throughout  the  area, 
except  in  the  northwestern  quarter.  An  important  area  lying  about 
5  miles  east  of  El  Centro  has  an  extent  of  some  10  square  miles. 
Another  is  mapped  about  2  miles  east  of  Holtville.  Other  areas  of 
varying  sizes  are  associated  with  soils  of  the  Imperial  and  the  Holt- 
ville series. 

In  its  natural  condition  this  type  was  slightly  hummocky,  and 
locally  marked  by  isolated  bodies  of  Dunesand.  Most  of  the  type 
has  been  leveled  for  irrigation  and  has  a  smooth,  gently  sloping 
surface. 

The  drainage  of  the  soil  is  slightly  deficient,  and  accumulations 
of  underground  or  seepage  water,  particularly  in  the  southeastern 
part  of  the  area,  are  developing  in  local  areas.  Narrow  areas  of  soil 
along  the  canals  already  have  become  too  wet  for  cultivated  crops. 

The  heavier  subsoil  material  of  this  type  in  most  places  contains 
more  than  0.20  per  cent  alkali,  and  the  quantity  in  many  places  is 
relatively  large.  The  surface  soil  is  free  from  alkali,  except  where 
seepage  or  a  high  water  table  has  caused  its  concentration  in  this  part 
of  the  profile. 

Alfalfa  and  grains  are  the  principal  crops  on  this  type.  (PI.  Ill, 
fig.  2. )  The  former  is  apparently  better  adapted  to  those  bodies  where 
the  heavy  subsoil  lies  several  feet  below  the  surface.  The  grains 
do  best  where  the  surface  soil  is  relatively  shallow. 


;_ 


FIELD  OPERATIONS   OF   Tin:   BUREAU    <•!■'   SOILS,  11)18. 


The  following  table  gives  the  average  results  of  mechanical 
analyses  of  samples  of  the  soil  and  subsoil  of  the  Mcloland  line 
sandy  loam  : 

Mechanical  analyse*  of  Meloland  fine  sandy  loam. 


Number. 

De    riptiim. 

Fine 
gravel. 

Coarse 
sand. 

Medium 

sand. 

Fine 

sand. 

Very  One 

sand. 

Silt. 

Clay. 

576001,57 

Soil 

Per  a  at. 

0.0 

.0 

I'ir  a  nl. 

0.2 

.'l 

I'ir  a  at- 

II.  1 
.1 

Per  cent. 
46.5 
17.3 

Per  cent. 
30.7 
26.9 

Per  cent. 
12.2 
35.0 

Per  cent. 
9.8 

576008,575044 

Subsoil 

20.6 

BOSITAS   GRAVELLY    FINE   BAND. 


The  surface  soil  of  Rositas  gravelly  fine  sand  is  a  light-brown, 
somewhat  compact  but  pervious  fine  sand,  containing  a  large  per- 
centage of  small  waterworn  gravel.  The  surface  soil  ranges  in 
depth  from  G  to  12  inches,  and  is  underlain  by  an  incoherent  yellow- 
ish-brown fine  sand  extending  to  a  depth  of  6  feet  or  more.  Both 
the  surface  soil  and  subsoil  are  calcareous,  but  no  concretions  or 
segregated  deposits  of  calcareous  material  are  present. 

This  type  is  restricted  to  a  few  small  areas  in  the  northeastern 
corner  of  the  area,  east  of  the  old  beach  line.  This  is  gently  rolling 
to  slightly  hummocky.  It  is  slightly  lower  than  that  of  the  old 
beach  line,  but  has  about  the  same  elevation  as  other  adjacent  soils. 

The  materials  composing  this  type  are  derived  from  the  old  sedi- 
mentary deposits  that  form  the  higher  desert  slopes  east  of  the  irri- 
gated part  of  this  valley.  Since  their  deposition,  the  surface,  which 
is  but  scantily  covered  with  vegetation,  has  been  subjected  to  the 
force  of  the  winds  for  a  very  long  period,  and  there  has  been  both 
a  reworking  and  a  removal  of  the  original  material.  As  a  result 
the  areas  are  dotted  with  mounds  and  marked  by  occasional  larger 
dunes.  Another  result  of  the  reworking  has  been  the  concentration 
of  gravel  in  places  on  the  surface,  so  that  typical  desert  pavement 
has  developed.  In  such  areas  the  larger  part  of  the  surface  ma- 
terial to  a  depth  of  2  or  3  inches  may  consist  of  gravel.  Drainage 
is  somewhat  excessive. 

None  of  this  type  is  under  cultivation  at  the  present  time,  as  it 
lies  entirely  above  the  present  supply  of  irrigation  water.  The  na- 
tive vegetation  is  largely  creosote  bush.  Under  irrigation  the  land 
should  prove  well  adapted  to  alfalfa. 


KOSITAS    SAND. 


The  Rositas  sand  consists  of  6  feet  or  more  of  a  slightly  pinkish, 
yellowish,  or  light  grayish  brown  medium-textured  incoherent  sand, 
of  1owt   organic-matter  content,  containing  in  many   places  small 


SOIL,   SURVEY   OF   THE  EL   CENTSO   AKliA,   CALIFORNIA.  43 

shells  and  calcareous  concretions.  The  only  variation  in  the  char- 
acter of  this  type  is  around  the  margins  of  the  bodies  where  it  grades 
into  a  heavier  member  of  the  Imperial  series,  and  in  such  locations 
a  compact  heavy  subsoil  is  present  at  depths  below  3  feet. 

The  surface  is  hummocky,  the  material  being  subject  to  movement 
with  every  wind.  It  is  identical  in  formation  with  Dunesand,  the 
only  difference  between  the  two  types  being  in  the  relatively  smoother 
topography  of  this  soil,  which  makes  it  possible  to  level  it  for  irri- 
gation and  cultivation. 

This  type  is  confined  to  the  western  part  of  the  area,  in  the  vicinity 
of  the  Main  West  Side  Canal,  in  Ts.  16,  16|,  and  17  S.,  and  largely 
in  R.  12  E. 

Alfalfa  occupies  the  largest  part  of  the  area  now  under  cultiva- 
tion. Some  small  grain,  cotton,  and  corn  are  also  grown,  but  the 
tendency  is  to  confine  those  crops  to  the  soils  of  series  having  heavier 
subsoils. 

ROSITAS  FINE  SAND. 

The  Rositas  fine  sand  consists  of  6  feet  or  more  of  a  light  yellow- 
ish brown,  or  light  grayish  brown  incoherent  fine  sand,  but  as 
mapped  in  this  survey  the  soil  in  small  areas,  most  commonly  in 
the  zone  of  gradation  into  the  heavier  textured  soils  of  the  Impe- 
rial series,  is  less  than  G  feet  deep,  and  a  heavier  subsoil  stratum 
occurs.  In  its  natural  condition  the  surface  of  this  type  is  marked 
by  hummocks  and  ridges  of  wind-blown  materials,  which  is  even 
now  more  or  less  unstable.  The  type  is  similar  to  the  soil  mapped 
as  Dunesand,  except  in  the  matter  of  unevenness  of  surface,  the 
Rositas  areas  showing  less  relief. 

This  type  is  developed  almost  exclusively  in  the  eastern  and 
western  parts  of  the  area,  adjacent  to  the  East  Side  High  Line  Canal, 
and  the  Main  West  Side  Canal,  where  it  is  associated  with  the  very 
fine  sand  of  this  series  and  with  Dunesand.  Outside  of  these  locali- 
ties, the  only  notable  body  is  found  between  the  Alamo  River  and  the 
Ash  Canal,  in  Ts.  16  and  17  S. 

This  type  is  devoted  largely  to  alfalfa,  to  which  it  is  apparently 
better  adapted  than  to  such  tilled  crops  as  cotton  and  corn,  for  the 
reason  that  it  affords  conditions  favorable  to  the  extensive  root  de- 
velopment of  that  plant.  Alfalfa  is  also  a  desirable  crop  in  that 
it  forms  a  permanent  cover  for  the  soil,  thus  preventing  the  (hill- 
ing of  the  surface  material  that  takes  place  in  areas  planted  to  annual 
crops. 


44 


FIELD  OPERATIONS   OF    l  in:    BUREAU    OF   soils,   T.U8. 


The  following  table  gives  the  results  of  mechanical  analysis  of 
a  sample  of  the  soil  of  the  Rositas  fine  sand: 

Mechanical  analysis  of  Rositas  fine  sand. 


Number. 

Description. 

Kino 
gravel. 

Coarse 
sand. 

Medium       Fine 

.sand.         sand. 

Very  fine 
sand. 

Silt. 

(lay. 

575024 

Soil 

l\r  cent. 

0.0 

Per  cent. 

0.0 

Per  a  nt.   Per  cent. 

0.3            54.5 

Per  cent. 

36.0 

Per  cent. 
4.6 

Per  cent. 
4.4 

ROSITAS    VEST    FINE    SAM). 

The  Rositas  very  line  sand  consists  of  6  inches  to  3  feet  of  a  some- 
what loamy  light  grayish  brown  to  light-brown  very  fine  sand, 
underlain  to  a  depth  of  6  feet  or  more  by  incoherent  sand,  fine  sand, 
and  permeable  fine  sandy  loam.  Both  soil  and  subsoil  are  slightly 
calcareous,  but  no  local  concentrations  of  lime  occur. 

Considerable  variation  in  both  the  texture  and  structure  of  the 
soil  and  subsoil  occurs  in  marginal  areas  of  the  type,  the  former 
merging  gradually  into  the  adjacent  soils  and  the  latter  containing 
in  many  places  strata  of  heavier  materials. 

Virgin  areas  of  this  soil  have  either  a  slightly  rolling  surface,  with 
small  accumulations  of  wind-blown  materials  around  the  bases  of 
shrubs,  or  a  decidedly  rolling  and  ridged  topography,  locally  dune- 
like. Within  the  irrigated  districts  of  the  area,  which  have  been 
leveled,  there  is  commonly  no  surface  difference  between  this  and  the 
adjacent  types,  except  locally  where  there  are  small  areas  of  wind- 
blown sand.  (PI.  IV,  Fig.  1.)  Within  the  areas  of  this  type  the  wind 
in  places  has  removed  the  soil,  forming  what  are  locally  known  as 
"  blowouts."  Some  of  the  smaller  "  blowouts "  have  been  filled  in 
and  are  now  cultivated,  but  the  surface  of  some  of  the  areas  is  so 
irregular  that  no  attempt  has  been  made  up  to  the  present  time  to 
reclaim  them.  A  notable  example  of  this  condition  is  in  the  district 
about  3  miles  southeast  of  El  Centro. 

A  few  areas  of  this  type,  in  the  vicinity  of  the  Main  West  Side 
Canal  and  southward  from  Dixieland,  constitute  practically  the  extent 
of  this  soil  in  the  western  half  of  the  area.  East  of  the  line  of  the 
Southern  Pacific  Railroad  there  are  a  few  small  areas  in  T.  15  S. 
The  largest  areas  occur  south  and  southeast  of  Holtville  and  south- 
east of  El  Centro,  and  a  number  of  smaller  bodies  are  distributed 
throughout  the  southeastern  part  of  the  area. 

The  drainage  of  this  type  is  naturally  good  to  slightly  excessive, 
but  there  are  a  few  places  in  the  vicinity  of  the  larger  canals  where 
the  soil  has  been  affected  by  seepage  or  by  a  rise  in  the  level  of  the 
water  table. 


SOIL   SURVEY   OF   THE   EL   CENTRO   AREA,   CALIFORNIA. 


45 


Practically  all  this  soil  contains  alkali  in  quantities  ranging  from 
0.2  to  1  per  cent,  the  salts  in  most  cases  being  uniformly  distributed 
throughout  the  soil  profile.  In  the  immediate  vicinity  of  the  larger 
canals,  where  some  seepage  occurs,  there  may  have  developed  an 
alkali  crust,  below  which  the  quantity  of  alkali  may  be  hardly  appre- 
ciable. As  with  all  the  soils  of  the  area,  excepting  the  wind-blown 
sands  and  fine  sands,  there  arejiere  and  there  spots,  in  many  cases  but 
a  few  feet  in  diameter,  where  the  quantity  of  alkali  is  sufficient  to 
prevent  the  growth  of  plants,  but  which  are  of  too  small  extent  to 
be  shown  on  the  soil  map. 

Nearly  all  this  type  is  under  cultivation,  the  largest  uncultivated 
body  being  that  in  the  "blowout"  region  southeast  of  El  Centre 
Most  of  the  crops  common  to  the  region  are  grown.  There  is  a  ten- 
dency to  use  the  areas  with  the  lighter  subsoil  for  alfalfa  and  to 
restrict  the  tilled  crops  to  areas  in  which  the  heavier  subsoil  occurs. 

The  following  table  gives  the  results  of  mechanical  analyses  of 
samples  of  the  soil  and  subsoil  of  the  Rositas  very  fine  sand : 

Mechanical  analyses  of  Rositas  very  fine  sa/nd. 


Number. 

Description. 

Fine 
gravel. 

Coarse 
sand. 

Medium 
sand. 

Fine 
sand. 

Very  fine 
sand. 

Silt. 

Clay. 

575021 

Soil 

Per  cent. 

0.0 

.0 

Per  cent. 

0.1 

.1 

Per  cent. 

0.1 

.2 

Per  cent. 
36.2 
41.3 

Per  cent. 
48.6 
44.4 

Per  cent. 
12.7 
7.0 

Per  cent. 
1.9 

575022 

Subsoil 

EOSITAS    VERY    FINE    SANDY    LOAM. 


The  soil  and  subsoil  material  of  the  Rositas  very  fine  sandy  loam 
to  a  depth  of  6  feet  or  more,  is  a  light  grayish  brown  very  fine  sandy 
loam  of  friable  structure  though  rather  heavy  texture,  the  propor- 
tion of  silt  being  relatively  large.  It  is  uniform  in  texture  through- 
out the  soil  profile,  except  that  in  the  lower  part  it  becomes  some- 
what compacted  and  therefore  less  pervious.  It  contains  a  fair 
amount  of  organic  matter  and  is  easily  cultivated.  The  soil  contains 
enough  alkali  to  have  a  serious  effect  on  its  use. 

Only  one  area  of  this  type  is  found  in  the  El  Centro  survey.  This 
is  situated  about  5  miles  northeast  of  Holtville  on  the  east  side  of  the 
Main  East  Side  Canal.  Viewed  as  a  whole  the  area  is  nearly  level, 
but  in  detail  the  surface,  before  it  has  been  leveled,  is  very  uneven, 
being  thickly  settled  with  circular  dimes,  ordinarily  5  to  8  feet  high, 
but  in  some  places  attaining  a  height  of  10  or  12  feet.  The  soil  in  the 
flats  or  hollows  between  the  dunes  is  a  trifle  heavier  than  the  soil  of 
the  dunes. 

There  is  no  erosion  in  this  soil  and  the  drainage  is  naturally  rather 
poor.    Waste  irrigation  water  from  higher  lying  ground  has  been  al- 


46  ni.LD  OPERATIONS  OF   THE  BUREAU   OF   SOILS,   1918. 

[owed  to  flow  across  it.  keeping  part  of  it  quite  wet.  After  leveling  it 
is  well  suited  to  irrigation. 

The  dunes  support  a  sparse  growth  of  mesquite  and  other  desert 
plants. 

Up  to  the  present  most  of  the  type  remains  in  its  virgin  condition, 
owing  apparently  to  the  high  cost  of  leveling  the  dunes  and  to  the 
uncertainty  of  crops  on  a  soil  of  such  a  high  alkali  content.  Part 
of  it.  that  having  the  least  alkali,  is  Ijeing  leveled  and  utilized  for 
crops,  the  yields  of  which  arc  low  to  moderate. 

CABRIZO    SAM). 

The  surface  soil  of  the  Carrizo  sand,  which  varies  from  6  to  12 
inches  in  depth,  is  a  light-gray  or  light  brownish  gray  sand,  ranging 
in  texture  from  coarse  to  rather  fine,  and  with  or  without  small  quan- 
tities of  small  waterworn  gravel.  The  soils  of  different  textures 
occupy  very  small  areas  and  it  is  not  possible  to  differentiate  them 
on  a  map  of  the  scale  used  in  the  present  survey.  This  has  caused 
their  grouping  under  the  one  name  Carrizo  sand.  The  subsoil,  the 
color  of  which  is  similar  to  that  of  the  surface  soil,  is  normally  a 
rather  coarse  sand  carrying  considerable  waterworn  gravel,  the  pro- 
portion of  the  latter  increasing  with  depth.  Both  soil  and  subsoil 
contain  small  amounts  of  lime  uniformly  distributed,  but  no  concre- 
tions or  other  accumulations  of  lime  or  cementing  of  the  soil  ma- 
terial by  lime  were  noted  in  the  course  of  the  survey. 

The  material  of  this  soil  has  been  deposited  by  several  desert  washes 
in  the  western  part  of  the  area.  The  discharges  of  these  streams  are 
intermittent  and  exceedingly  irregular,  and  with  every  flow  of  water 
the  soil  is  subject  to  alteration  in  texture  and  structure  either  by 
erosion,  deposition,  or  a  reworking  of  the  material  already  in  place. 

This  type  occurs  in  long,  narrow  bodies,  somewhat  depressed  below 
the  level  of  the  adjacent  soils,  and  occupying  local  flood  plains  of 
desert  streams,  or  as  rather  extensive  gently  sloping  alluvial  fans. 

Xone  of  this  soil  is  under  cultivation  at  present,  and  its  possible 
agricultural  value  is  low.  In  the  northern  part  of  T.  16  S.,  R.  11 
E.,  the  soil  occupies  the  broad  floor  of  a  desert  wash,  which  at  fre- 
quent and  irregular  intervals  may  be  completely  covered  with  water 
for  brief  periods.  In  the  other  bodies  of  this  soil  the  streams  have 
developed  no  permanent  channels,  but  have  laced  the  surface  with  a 
network  of  shallow,  poorly  defined  courses.  The  discharge  of  these 
streams  would  necessarily  have  to  be  confined  to  permanent  channels 
before  the  land  could  be  used,  and  the  construction  of  such  works 
and  their  maintenance  would  be  an  expensive  undertaking.  In  addi- 
tion, the  soil  would  require  large  quantities  of  irrigation  water, 
owing  to  the  open,  porous  subsoil.    Under  irrigation  this  soil  would 


SOIL  SURVEY   OF   THE   EL   CENTRO   AREA,   CALIFORNIA.  47 

probably  be  better  adapted  to  ,alfalfa  than  to  the  grains  or  tilled 
crops  commonly  grown  in  this  region. 

RIVERWASH. 

The  material  mapped  as  Riverwash  in  the  El  Centro  area  is  not 
typical,  in  that  it  is  free  from  gravel  and  coarse  sand  and  consists 
of  a  succession  of  thin  strata  composed  of  fine  sand,  silt,  and  clay, 
resting  upon  a  deep  substratum  of  compact  clay. 

The  type  is  located  within  the  narrow  flood  plain  of  New  River, 
where  it  has  been  deposited  since  the  recent  erosion  of  the  present 
valley  of  that  stream.  The  soil  is  subject  to  continual  alteration  and 
reworking  during  overflow  of  the  river,  and  parts  of  it  are  being 
slowly  buried  beneath  accumulations  of  materials  carried  by  the  wind 
from  the  higher  lands.    The  drainage  is  deficient. 

Owing  to  the  unfavorable  drainage  conditions,  the  danger  of  over- 
flow, and  the  impracticability  of  economically  reclaiming  these  lands 
under  present  conditions,  this  type  has  no  immediate  agricultural 
value,  and  its  only  value  lies  in  the  scanty  pasturage  it  affords. 

ROUGH    BROKEN    LAND. 

Rough  broken  land  consists  of  soil  materials  representing  a  variety 
of  soil  series,  the  topography  of  which  is  too  uneven  and  broken  to 
allow  their  use  for  agriculture. 

In  this  survey  Rough  broken  land  includes  the  eroded  areas  in  the 
western  part  of  the  survey  in  the  vicinity  of  the  Yuha  Buttes  and 
around  the  margins  of  the  irregular  mesa  occupied  by  the  Tijeras 
gravelly  fine  sandy  loam.  It  also  comprises  narrow  bodies  consisting 
of  the  slopes  of  some  of  the  valleys  of  the  larger  desert  streams 
and  the  rough  and  eroded  areas  of  the  Superstition  Mountains  lying 
within  the  survey.    It    rarely  occurs  in  ,any  other  parts  of  the  area. 

DUNESAND. 

The  type  Dunesand  consists  of  6  feet  or  more  of  fine  or  very  fine 
sand,  occurring  in  hummocks  and  dunes  so  large  that  they  can  not 
be  economically  leveled  and  thus  made  suitable  for  irrigation  and 
cultivation.  These  dunes  usually  are  devoid  of  vegetation,  except 
for  small  desert  shrubs  around  their  bases,  or  partly  buried  but  still 
living  mesquite  trees,  arrowweed,  or  creosote  bushes. 

Dunesand  is  most  extensively  developed  east  and  west  of  central 
irrigated  parts  of  the  area,  where  it  occurs  either  as  isolated  dunes, 
or  as  nearly  continuous  areas  of  drifting  sand.  Within  the  central 
part  of  the  area,  south  of  Holtville,  there  is  one  rather  extensive 
area  of  Dunesand,  but  its  usual  occurrence  is  as  smaller  bodies  scat- 
tered through  areas  of  other  types  of  soil.  Practically  all  of  this 
material  is  unstable  and  with  every  severe  storm  the  dunes  move 


Is  FIELD   OlMHATIoNS    or    THE   BURKAT    OF    SOILS,    1018. 

a  distance  of  several  feet.  This  movement  is  largely  to  the  east, 
and  is  -lowly  burying  the  native  vegetation  and  the  cultivated  crops 
in  front  of  it.    The  land  is  not  utilized  and  has  no  agricultural  value. 

[KRIGATION. 

The  possibilities  of  irrigating  this  region  were  apparently  first 
realized  by  a  western  traveler  in  1849,  and  10  years  later  the  Cali- 
fornia Legislature  passed  an  act  ceding  all  the  State  rights  in  the 
land  to  an  individual  who  proposed  to  place  the  land  under  irri- 
gation. The  unsettled  conditions  just  prior  to  the  Civil  War  com- 
manded the  attention  of  the  United  States  and  the  consent  of  the 
Federal  Government  to  the  above  arrangement  could  not  be  obtained. 
The  matter  of  irrigating  these  lands  again  attracted  some  attention 
at  the  time  of  the  construction  of  the  Southern  Pacific  Railroad  from 
Yuma  to  Los  Angeles,  in  1879,  but  it  was  not  until  about  1892  that 
the  first  field  survey  was  made.  In  1900  work  was  begun  on  a  di- 
version and  distributing  system  by  the  California  Development  Co., 
and  in  1902  the  first  water  was  available  for  some  of  the  lands  north 
of  the  international  boundary.  The  rapidity  of  the  development  in 
this  region  is  evident  from  the  fact  that  in  1909.  seven  years  after 
the  first  water  was  available,  there  had  been  constructed  main  and 
lateral  canals  with  a  total  length  of  1,007  miles  and  190,711  acres 
of  land  had  been  brought  under  irrigation.4  Four  years  later  (1913) 
there  were  about  264,000  acres  under  irrigation.5 

The  development  of  this  project  was  continued  by  the  California 
Development  Co.  for  several  years.  Financial  difficulties  resulted 
in  the  acquiring  of  the  system  by  the  Southern  Pacific  Railroad  Co., 
and  later  it  was  purchased  by  the  farmers  and  is  now  owned  and 
controlled  by  them  under  the  name  of  the  Imperial  Valley  Irrigation 
District.  This  organization  confines  itself  solely  to  maintaining 
the  diversion  works  and  main  distributing  canals,  and  with  dis- 
tributing water  to  the  several  mutual  water  companies,  the  de- 
livery of  water  to  the  consumers  being  effected  through  the  latter 
organizations.  These  pay  50  cents  per  acre-foot  (measured  at  the 
point  of  diversion)  and  the  water  is  delivered  to  the  users  at  the 
rate  of  50  cents  per  acre-foot  for  each  24  hours,  in  addition  to  which 
annual  assessments  are  levied  against  the  lands  in  each  district  to 
meet  the  expenses  of  maintaining  an  administrative  force,  main- 
taining canal  structures,  and  removing  deposits  of  silt  from  the 
canals.     (PI.  IV,  Fig.  2.) 

1  T".   S.  Census,  1910. 

"  W.   S.    Paper  \o.  39o,  p.  44,  D.   S.   Geological   Survey. 


Report  of  Bureau  of  Soils,  U.  S.  Dept.  of  Agriculture,  1918. 


PLATE    III. 


£.9741 

Fig.   !. — Imperial  Silty  Clay  Prepared  for  Planting  to  Muskmelons. 


A'i 


""^^SH^S 

*♦  '   v.*.    " 

~vwfv 

•  ^i&&>         i»       ■**■' 

•  ^■d&BSSSIO&Lii  '■  \*Vi 

k-v**.              '& 

^^^^SSS^^^^^tMK^ 

Fig.  2. — Alfalfa  Grown  as  a  Soiling  Crop  on  Meloland  Fine  Sandy 

Loam. 

This  crop  was  ready  to  cut  January  5. 


•  ot  Bureau  of  Soils.  U.  S.  Dept.  of  Agriculture,  1918. 


PLATE     IV. 


F13.    I. — Rositas  Very  Fine  Sand  near  Holtville. 

With  the  exception  of  the  one  large  dune  in  the  foreground,  which  has  been  left  on  account  of 
cost  of  leveling,  this  area  ha-;  been  leveled  for  irrigation.    The  crop  is  alfalfa. 


JV-- 


'  "■■•  ■%?- 


Fig.  2. — View  Looking  Down  Roadway,  Showing  Wall  of  Silt 
Removed  from   Irrigation  Canal  on  Left. 

Removal  of  this  material  is  a  troublesome  problem  in  connection  with  irrigation  in 


Deposits 

this  valley. 


SOIL  SURVEY  OF   THE   EL  CENTRO   AREA,   CALIFORNIA.  49 

All  the  water  used  for  the  irrigation  of  this  area  is  supplied  by 
the  Colorado  River,  which  has  a  watershed  of  about  244,000  square 
miles,  and  a  mean  annual  run-off  of  about  17,000,000  acre-feet.6 

The  water  is  diverted  from  the  Colorado  River  at  the  Hanlon 
Heading,  a  few  hundred  yards  north  of  the  international  boundary 
line,  and  about  7  miles  by  river  below  Yuma,  Ariz.  The  main  canal 
enters  Mexican  territory  and  extends  westward  for  about  50  miles 
to  Sharps  Heading,  where  several  smaller  canals  carry  water  north 
across  the  international  boundary  line  to  the  eastern  and  central 
parts  of  the  El  Centro  area  and  adjacent  lands  on  the  north.  Other 
canals  distribute  water  to  the  western  side  of  the  valley. 

Difficulties  in  successful  diversion,  owing  to  the  unstable  nature 
of  the  channel  of  the  river,  have  at  times  resulted  in  a  shortage  of 
irrigation  wate"  and  measures  are  now  being  taken  to  provide  for  a 
permanent  and  adequate  supply. 

Late  in  1904  an  unusually  heavy  flood  in  the  Colorado  River  cut 
through  the  heading,  and  in  the  summer  of  1905  and  1906  the  entire 
flow  of  that  stream  turned  northward  and  flowed  into  the  Salton 
Sink.  This  break  in  the  river  bank  was  closed  in  190G,  and  since 
that  time  the  flood  waters  of  the  river  have  flowed  to  the  Gulf  of 
California. 

The  records  of  delivery  of  water  during  1915  show  that  about  75 
per  cent  of  the  annual  amount  was  supplied  from  April  to  Sep- 
tember, inclusive.  During  the  winter  months  the  delivery  was 
about  4  per  cent  of  the  annual  amount,  the  water  at  that  time  of 
the.  year  being  used  largely  for  stock  and  domestic  purposes.  Dur- 
ing that  year,  when  there  was  a  shortage  of  water  during  some 
of  the  summer  months,  the  duty  of  water  throughout  the  district 
was  reported  to  have  been  2.72  acre-feet. 

The  amount  of  water  needed  for  crops  will  vary  with  the  crop  and 
the  physical  character  of  the  soil,  so  that  figures  for  any  given  part 
of  the  valley  may  be  totally  useless  if  used  as  a  basis  for  the  calcula- 
tion of  the  needs  of  another  part.  The  following  data  give  some 
indication  of  the  amounts  of  water  applied  in  the  culture  of  the 
various  crops.  The  superintendent  of  Water  Co.  No.  1  states  that 
the  average  amount  of  water  applied  per  acre  to  the  different  crops 
in  1912  was  as  follows:7  Alfalfa,  4.19  acre-feet;  corn,  2.18;  musk- 
melons,  1.C2;  and  barley,  1.00.  With  the  exception  of  alfalfa,  all  the 
crops  occupy  the  ground  for  but  a  part  of  the  year;  this  explains  in 
part  their  smaller  requirements.  Water  Co.  No.  7  reported  in  1907 
that  alfalfa  required  from  3.50  to  4.00  acre-feet. 

8U.  S.  Geological   Survey,  W.   S.  Paper  No.   395,   p.   23. 

7  Fourth  Biennial  Report,  Dept.  of  Engineering,  State  of  California.     1912  (<>  1.914. 


50  I  II  l  D  OPERATIONS   OT   Till'.   BTJREAU   OF  SOILS,  1!)18. 

Tilled  crops  such  as  cotton,  corn,  and  truck  crops  are  irrigated  by 
the  I'lirmw  method;  alfalfa,  grain,  and  grass  fields  are  divided  into 
long  narrow  shallow  basins  locally  known  as  "lands,"  which  are 
Hooded  at  proper  intervals. 

In  considering  the  possible  future  results  of  continued  irrigation 
on  the  soils  of  this  area  only  a  very  general  statement  can  be  made 
owing  to  the  ever  variable  nature  of  the  subsoil  conditions,  and  time 
may  prove  that  any  present  prediction  will  fall  short  of  the  actual 
conditions  that  may  develop. 

For  the  purpose  of  discussion  the  soils  may  be  divided  into  a  num- 
ber of  genera]  groups.  The  first  of  these  would  include  the  soils  of 
the  Imperial  series  and  those  bodies  of  the  types  of  the  Meloland 
series  where  the  surface  soil  is  very  shallow.  In  these  soils  the  char- 
acteristic feature  of  the  subsoils  is  a  heavy  texture  ranging  from  silty 
clay  loam  to  heavy  clay,  with  which  is  associated  a  condition  of  very 
compact  structure.  Such  soils  permit  only  a  slow  gravity  or  capil- 
lary movement  of  moisture  and  ordinarily  take  up  but  little  water, 
and  in  many  cases  it  has  been  found  that  after  a  season's  irrigation 
the  subsoil  was  still  air  dry  below  a  depth  of  24  inches.  It  has  also 
been  found  in  fields  which  had  been  irrigated  throughout  the  pre- 
vious season  that  in  January  the  soil  was  practically  air  dry  through- 
out its  entire  depth.  Unfavorable  moisture  conditions  will  appear 
but  slowly  in  these  soils,  but,  when  once  developed,  the  impervious 
subsoil  will  make  reclamation  a  difficult  matter. 

In  the  second  group  may  be  included  all  the  soils  of  the  Rositas 
series,  the  areas  of  the  Holtville  series  having  thin  or  shallow  sur- 
face soils  and  the  areas  of  the  Meloland  soils  having  deep  surface 
soils.  In  the  first  two  series  the  textures  of  the  subsoils  are  light, 
i.  e..  light-textured  silt  loams  or  fine  sandy  loams  to  sands.  In  the 
Rositas  series  both  the  soil  and  subsoil  absorb  moisture  rapidly  and 
any  excess  of  moisture  moves  into  the  deeper  subsoil  until  arrested 
or  retarded  by  meeting  a  substratum  of  heavier  material.  In  the 
shallower  members  of  the  Holtville  series  any  moisture  reaching  the 
subsoil  is  widely  distributed  throughout  its  mass  and  removed  from 
the  effects  of  surface  evaporation.  In  the  deeper  surface  soils  of  the 
Meloland  series  the  surface  soil  takes  up  moisture  readily,  and  when 
this  has  penetrated  to  the  heavier  subsoil  it  may  be  beyond  the  reach 
of  the  effects  of  surface  evaporation.  In  this  group  the  effect  of  con- 
tinued irrigation  upon  conditions  of  subdrainage  will  depend  upon 
the  ability  of  the  subsoils  to  remove  any  excessive  amounts  of  sub- 
surface waters,  and  the  development  of  unfavorable  conditions  of 
subdrainage  will  probably  not  arise  over  any  large  and  extensive 
areas. 

In  the  third  group  may  be  included  the  very  light  textured  soils 
of  the  Superstition  series  and  associated  types  above  the  present 


SOIL   SURVEY  OF   THE   EL,  CENTRO  AREA,   CALIFORNIA.  51 

canal  system.  When  placed  under  irrigation,  the  larger  part  of 
these  soils  will  probably  remain  permanently  free  from  the  accumu- 
lations of  excessive  amounts  of  subsurface  or  drainage  water.  Un- 
less artificial  drainage  be  provided,  however,  there  will  tend  to  be 
eventually  developed  a  water-logged  area  below  and  adjacent  to 
and  roughly  parallel  to  the  present  high  line  canals,  as  the  subsoil 
drainage  waters  from  these  pervious  soils  of  the  desert  slopes  will 
there  meet  the  heavier  subsoils  of  the  Imperial  and  Meloland  series, 
and  be  brought  to  the  surface. 

Certain  areas  with  high  water  table,  water-logged  subsoils,  or 
other  evidence  of  retarded  subdrainage  have  existed  for  several 
years,  and  according  to  reports,  these  areas  are  slowly  increasing 
from  year  to  year.  It  appears  that  this  condition  may  be  due,  in 
part  at  least,  to  loss  of  water  by  seepage  through  the  canal  banks. 

While  deposition  in  the  canals  and  ditches  of  large  amounts  of 
silt  carried  in  suspension  by  the  irrigation  waters  is  having  some 
effect  in  retarding  the  loss  of  water  by  seepage,  it  is  probable  that 
in  certain  localities  only  lining  canals  with  concrete  will  effectually 
remedy  the  situation.  Such  means  of  prevention,  with  exercise  of 
greater  care  and  caution  in  the  use  of  irrigation  water  and  a  more 
or  less  comprehensive  system  of  drainage,  will  be  the  only  effective 
means  of  improving  the  soils  now  so  adversely  affected,  and  in  pre- 
venting the  extension  of  the  injury  to  unaffected  areas. 

ALKALI. 

During  the  process  of  decomposition  and  disintegration  of  rocks 
and  rock  fragments  in  the  formation  of  soils,  certain  minerals  and 
mineral  compounds  are  dissolved  by  the  percolating  waters.  In 
regions  where  the  rainfall  is  sufficient  to  leach  these  materials  from 
the  soils  and  to  maintain  a  movement  of  water  through  the  soil  and 
subsoil,  these  soluble  materials  do  not  accumulate  in  sufficient 
amounts  to  be  detrimental  to  the  growth  of  cultivated  crops.  In 
regions,  however,  where  the  rainfall  is  not  sufficient  to  leach  and 
carry  the  dissolved  substance  away  from  the  soil,  they  tend  to  ac- 
cumulate until  the  amount  becomes  sufficient  either  seriously  to 
retard  or  altogether  prevent  the  growth  of  crops. 

Such  excessive  accumulations  of  soluble  material  are  localized  or 
brought  about  by  the  gradual  evaporation  of  ground  or  surface 
waters  from  localities  of  arrested  drainage  or  inclosed  basins  which 
have  no  drainage  outlet.  Such  conditions  exist  quite  commonly 
throughout  the  western  part  of  the  United  States. 

All  that  portion  of  the  El  Centro  area  below  the  line  of  the  old 
beach  probably  was  formerly  a  northern  extension  of  the  present 
Gulf  of  California,  from  which  it  was  cut  off  by  the  development  of 
a  delta  ridge  by  the  Colorado  River  and  changed  to  an  inland  lake. 


52  FIELD  OPERATIONS  OF  THE  BUREAU   OF  SOILS,  1918. 

The  continued  evaporation  of  waters  which  found  their  way  into 
this  depression  lias  resulted  in  the  deposition  in  the  soils  of  the 
material  carried  in  solution,  which  today  forms  the  bulk  of  the 
alkali  that  is  present  in  this  area. 

Under  the  normal  desert  conditions,  there  has  probably  been  but 
little  recent  change  in  the  distribution  of  the  alkali  salts  in  these 
soils.  In  the  northeastern  part  of  the  survey  there  is  an  area  in 
which  there  is  apparently  a  slow  movement  of  subsoil  moisture  from 
the  higher  desert  regions  to  the  east,  which  has  resulted  in  the  de- 
velopment of  several  hundred  acres  of  alkali  land  in  which  the 
amount  of  salt  is  too  high  to  allow  the  growth  of  cultivated  crops, 
in  many  places  the  land  being  devoid  of  even  the  most  alkali  resist- 
ant vegetation. 

The  soluble  mineral  compounds  formed  or  set  free  during  the 
decomposition  of  rocks  and  soils  include  sulphate,  chloride,  car- 
bonate, and  bicarbonate  salts  of  calcium,  magnesium,  and  sodium. 
The  principal  salts  found  in  alkali  accumulations  are:  Sodium  sul- 
phate (Glauber's  salts),  sodium  chloride  (common  'salt'),  sodium 
bicarbonate  (baking  soda),  and  magnesium  sulphate  (Epsom  salts). 
Calcium  carbonate  (lime)  is  usually  present  in  variable  amounts,  and 
calcium  sulphate  (g37psum)  or  sodium  carbonate  (sal  soda)  is  present 
in  many  localities.  All  these  salts  excepting  the  last  usually  form 
white  crusts  upon  the  surface  of  the  soil  when  present  in  large 
amounts  and  are  commonly  spoken  of  as  "  white  alkali."  When  the 
last-named  salt  occurs  in  the  presence  of  organic  matter  and  moisture 
its  presence  is  usually  indicated  by  a  dark-brown  or  black  stain  or 
crust  on  the  surface  of  the  soil,  and  "  black  alkali  "  is  said  to  be 
present.  Other  substances  tend  to  produce  this  same  discoloration, 
and  the  stain  is  not  always  a  definite  indication  of  the  presence  of 
black  alkali. 

Alkali  salts  undergo  movement  or  translocation  only  when  there  is 
a  movement  of  moisture  in  the  soil,  and  the  rate  of  such  movement 
is  dependent  both  upon  the  amount  of  moisture  present  and  upon 
the  texture  and  structure  of  the  soil.  Other  things  being  equal,  the 
more  rapid  the  movement  of  water  through  the  soil  the  more  rapid 
is  the  movement  of  alkali  salts  from  place  to  place.  In  light-textured 
soils  water  moves  quite  rapidly  either  laterally  or  vertically,  depend- 
ing largely  upon  the  structure  of  the  soil,  and  this  in  part  explains 
the  sudden  appearance  of  alkali  in  such  soils  after  some  years  of 
irrigation,  while  near-by  heavier  textured  soils  apparently  show  no 
accumulations.  Alkali  salts  are  brought  to  the  surface  by  the  capil- 
lary movement  and  evaporation  of  moisture  from  the  soil,  where 
they  are  accumulated  or  concentrated  at  or  near  the  surface  and 
frequently  appear  as  "  alkali  crusts."  Alkali  salts  will  also  move 
laterally  if  the  occurrence  of  the  percolating  subsurface  waters  and 


SOIL  SURVEY   OF   THE   EL   CENTRO   AREA,    CALIFORNIA.  53 

the  structure  of  the  soil  are  such  as  to  favor  a  movement  of  moisture  in 
that  direction,  and  under  such  conditions  alkali  may  develop  in  dis- 
tricts far  removed  from  any  apparent  source  of  such  material. 

Alkali  may  or  may  not  be  apparent  from  the  surface  indications, 
but  its  presence  in  considerable  amounts  is  usually  indicated  either 
by  the  nature  of  the  vegetation,  by  a  puffy  or  mulch-like  appearance 
of  the  surface  soil,  or  by  the  presence  of  salt  crusts  on  the  surface 
of  the  ground.  Upon  irrigated  lands  a  stunted,  yellow  or  spotted 
growth  of  crops  and  the  presence  of  alkali-resistant  weeds  and 
grasses  are  practically  unfailing  signs  that  dangerous  amounts  of 
alkali  are  present  in  the  soil.  It  occasionally  happens  in  the  arid 
regions  that  the  presence  of  alkali  is  masked  to  a  large  extent,  and 
only  an  extensive  series  of  tests  to  a  depth  of  several  feet  can  de- 
termine the  location  and  concentration  of  alkali  deposits  present. 

The  harmfulness  of  alkali  is  dependent  not  only  upon  the  amount 
present  in  the  soil  but  upon  its  location  in  the  soil  profile,  its  chemical 
composition,  the  texture  of  the  soil,  and  the  amount  of  moisture  that 
may  be  present,  and  it  is  often  a  difficult  matter  to  determine  just 
which  of  these  conditions  are  most  potent  in  the  various  localities  in 
which  damage  may  have  resulted. 

Generally  speaking,  concentrations  of  alkali  of  over  1  per  cent  (by 
weight  of  dry  soil)  are  not  tolerated  by  any  cultivated  crop;  0.6  per 
cent  is  usually  tolerated  by  some  of  the  native  and  cultivated  grasses, 
sugar  beets,  some  of  the  sorghums,  and  barley;  0.4  per  cent  is  ordi- 
narily not  too  high  a  concentration  to  allow  the  growth  of  alfalfa, 
the  cereals  (except  Indian  corn),  cotton,  and  many  of  the  root  crops; 
and  0.2  per  cent  is  usually  insufficient  to  affect  the  growth  of  any 
ordinary  field  crops.  The  percentages  given  above  presuppose  that 
the  alkali  salts  are  uniformly  distributed  throughout  the  soil  profile. 
This  is  seldom  the  case,  as  the  salts  tend  to  concentrate  at  various 
horizons  depending  upon  the  moisture  conditions  and  the  texture  of 
the  soil  and  subsoil  material.  The  amounts  of  alkali  that  plants  can 
withstand  are  very  much  lower  than  the  above  figures  when  the 
alkali  is  concentrated  upon  or  near  the  surface. 

The  white  alkali  salts  vary  in  degree  of  harmfulness,  according  to 
their  composition.  The  chloride  salts  are  generally  considered  the 
most  harmful,  the  sulphates  are  somewhat  less  so,  and  the  bicarbon- 
ates  seem  to  have  very  little  effect.  The  latter  salts,  however,  are 
undesirable,  since  if  present  in  considerable  amounts  they  may  under- 
go a  chemical  change  and  form  the  very  dangerous  black  alkali. 
This  is  very  serious  for  practically  all  cultivated  crops  when  there 
is  more  than  0.05  per  cent  of  it  in  the  soil. 

Other  things  being  equal,  the  degree  of  alkali  injury  is  largely  de- 
termined by  the  amount  of  moisture  in  the  soil.  With  a  given  per- 
centage of  alkali  present,  the  strength  of  the  solution  in  the  soil 


.VI  ii it  1 »  OPERATIONS  Of  Tin:   BtTREATJ   OF  SOILS,  1918. 

varies  with  the  moisture  content,  and  a  crop  thriving  in  a  very  moist 
soil  may  be  entirely  killed  by  the  removal  of  a  large  part  of  the 
moisture,  through  the  concentration  of  the  solution  of  salts. 

During  this  survey,  in  the  determination  of  the  amount  of  alkali 
an. I  its  location  in  the  soil,  frequent  borings  were  made  with  a  soil 
auger  to  a  depth  of  6  feet.  The  samples  thus  obtained  were  usually 
divided  into  foot  sections,  and  the  amount  of  alkali,  expressed  in 
terms  of  percentage  of  total  salts  in  the  air-dry  soil,  was  determined 
in  each  section  by  measuring  the  electrical  resistance  of  the  soil  with 
an  instrument  especially  devised  for  this  purpose.  The  total  of  the 
amounts  of  alkali  in  the  several  sections,  divided  by  the  number  of 
the  sections,  is  taken  as  the  average  amount  of  alkali  in  the  soil  to 
the  depth  of  the  boring. 

When  alkali  is  present  in  the  soil  to  a  harmful  degree,  the  only 
permanent  and  entirely  satisfactory  remedy  is  to  remove  it  by  drain- 
age and  leaching.  The  effect  of  this  operation,  if  thorough,  is  to 
wash  it  down  through  and  out  of  the  soil,  thus  permanently  remov- 
ing it  from  the  reach  of  the  plant  roots.  Where  alkali  is  present 
in  the  soil  in  moderate  amounts,  and  artificial  drainage  is  not  feasi- 
ble, the  best  use  may  be  made  of  the  land  by  selecting  such  crops 
as  are  most  tolerant  to  small  amounts  of  alkali,  and  practicing  such 
methods  of  tillage  as  will  tend  to  reduce  the  evaporation  of  moisture 
and  concentration  of  the  salts  in  the  surface  soil.  No  reliance  should 
be  placed  in  the  rather  common  belief  that  certain  crops  will  remove 
alkali  from  the  soil  in  sufficient  quantities  to  improve  it  so  that  less 
resistant  crops  can  safely  be  grown.  Temporary  improvement  noted 
under  such  conditions  will  usually  be  found  to  be  due  to  changed 
or  improved  methods  of  cultivation  and  irrigation,  which  have  for 
the  time  being  brought  about  desirable  physical  changes  in  the  soil, 
or  have  driven  the  alkali  into  the  deeper  soil.  The  alkali  content  has 
not  been  materially  reduced,  and  a  return  to  the  former  crops  and 
methods  of  cultivation  will  result  in  a  return  of  the  alkali  to  the 
surface. 

The  results  of  several  hundred  tests  show  that  alkali  is  quite  gen- 
erally present  in  all  of  the  soils  of  the  area,  excepting  those  which 
have  been  formed  mainly  by  the  action  of  the  wind,  and  certain 
other  light-textured  soils  upon  the  floor  of  the  desert  above  the 
present  irrigation  canals.  Aside  from  the  area  of  soil  in  the  north- 
eastern portion  of  the  area,  which  is  not  directly  comparable  with 
the  rest  of  the  area,  the  larger  areas  of  alkali  land  are  found  in  the 
central  parts  of  the  area  and  extending  westward  from  El  Centro 
and  Imperial  to  a  short  distance  beyond  New  River. 

In  mapping  the  alkali  of  the  area  the  lands  have  been  classed  in 
four  grades,  with  reference  to  alkali  content  and  visible  conditions, 


SOIL  SURVEY   OF   THE   EL   CENTRO   AREA,    CALIFORNIA.  55 

the  limits  of  each  grade  being  determined  partly  by  the  total  content 
of  salts  within  the  6-foot  section,  and  partly  by  the  appearance  and 
character  of  the  crop. 

The  lands  in  the  first  grade  may  be  considered  as  alkali  free,  since 
they  contain  less  than  0.2  per  cent  of  salts  distributed  in  such  a 
manner  as  to  have  caused  no  apparent  effect  on  plant  growth.  This 
grade  is  rather  inextensive  and  is  confined  mainly  to  the  area  of 
wind-blown  soils  along  the  margins  of  the  desert  and  to  a  number  of 
small  bodies  south  and  east  of  El  Centro  and  south  of  Holtville.  This 
grade  includes  some  of  the  most  desirable  tracts  of  land  in  the  El 
Centro  area,  and  if  properly  handled  no  damage  from  alkali  need 
be  feared. 

The  lands  of  the  second  grade  constituting  slightly  affected  areas 
contains  between  0.2  and  0.6  per  cent  of  salts  so  distributed  as  to  have 
no  visible  effect  on  crops.  While  these  lands  carry  somewhat  more 
alkali  than  the  lands  of  the  first  grade,  they  have  to  the  present  time 
produced  practically  as  good  crops.  With  the  higher  content  of  alka  1  i , 
however,  greater  care  is  necessary  in  handling  them,  as  improper 
management  may  cause  the  salts  to  concentrate  near  the  surface  and 
thus  to  injure  crops.  This  grade  is  extensive,  occupying  31  per  cent 
of  the  El  Centro  area.  It  includes  much  of  the  country  adjacent  to 
El  Centro  and  Holtville  and  considerable  areas  between  El  Centro 
and  Calexico. 

The  lands  of  the  third  grade,  constituting  moderately  affected 
areas,  include  lands  having  less  than  2  per  cent  of  salts,  distributed  in 
such  a  manner  as  to  have  a  visible  effect  on  crops,  but  not  to  prohibit 
agriculture.  Where  the  larger  quantities  of  salts  are  present,  they  are 
invariably  concentrated  in  the  lower  part  of  the  soil  section  or  beyond 
the  reach  of  the  roots  of  ordinary  crops.  On  the  other  hand,  where 
only  a  small  percentage  of  salts  occur,  these  are  concentrated  at  or 
near  the  surface,  where  their  influence  on  plant  growth  is  felt.  Crops 
on  lands  throughout  this  grade  are  spotted  and  the  yields  are  lower 
than  those  obtained  from  the  lands  of  the  preceding  grades.  This 
grade  of  land  is  extensive  in  the  El  Centro  area.  It  includes  for  the 
most  part  soils  of  heavy  texture  and  especially  types  with  heavy  sub- 
soils. The  largest  areas  lie  in  the  northern  part  of  the  area,  near  El 
Centro  and  east  and  west  of  Imperial.  Inasmuch  as  alkali  is  already 
affecting  crops  on  these  areas,  the  lands  of  this  grade  demand  careful 
handling  in  order  to  prevent  the  further  concentration  of  salts  near 
the  surface. 

The  fourth  grade  of  lands  comprise  the  strongly  affected  areas. 
The  total  salt  content  varies  greatly,  some  of  the  areas  in  this  class 
containing  only  a  small  percentage  of  salts  which  have  accumulated 
on  the  surface  and  prevented  plant  growth,  while  in  other  areas  the 


56  F1K1.P   OPERATIOTTS   OF   THE  BUREAU   OF   SOILS,  1918. 

alkali  may  be  distributed  in  high  concentrations  throughout  the  soil 
profile.  As  a  rule,  the  lands  of  (his  grade  are  easily  distinguished 
by  the  presence  of  a  white  crust  upon  the  surface,  by  brown  dis- 
colorations  on  the  surface  which  remain  moist,  by  the  absence  of 
vegetation,  or  by  a  very  poor  crop  growth.  In  a  few  instances,  as 
wot  of  Imperial,  the  surface  shows  no  indication  of  alkali,  even 
though  the  total  salt  content  in  the  G-foot  section  is  more  than  3  per 
rent.  Throughout  this  grade  the  lands  are  so  strongly  affected  that 
profitable  yields  of  the  ordinary  crops  can  not  be  produced.  Aside 
from  the  rather  extensive  body  west  of  Imperial,  strongly  affected 
areas  occur  along  New  River  cut,  throughout  the  heavy  clays  north- 
west of  Seeley,  and  under  the  East  Side  High  Line  Canal. 

Within  the  area  of  alkali  land  in  the  northeastern  portion  of  the 
survey,  and  over  much  of  the  territory  between  Imperial  and  New 
River,  the  soils  have  but  little  apparent  value  until  some  means  shall 
be  taken  to  remove  the  alkali.  Over  the  rest  of  the  area  included 
in  the  survey,  where  there  is  any  alkali  in  the  soil,  the  future  pro- 
ductivity of  such  lands  is  quite  closely  related  with  the  movement  of 
the  irrigation  and  subsurface  waters.  As  long  as  a  large  part  of 
the  excess  water  applied  to  the  fields  can  continue  to  move  down- 
ward through  the  soil  and  out  to  drainage  channels,  the  amount  of 
alkali  within  the  reach  of  the  plant  roots  probably  will  not  materially 
increase.  When,  however,  natural  drainage  can  not  remove  the  ex- 
cess of  water,  as  is  already  the  case  in  the  various  seepage  areas  men- 
tioned above,  the  alkali  will  constantly  increase  until  the  land  be- 
comes practically  worthless. 

The  facility  with  which  lands  may  be  reclaimed  from  alkali  de- 
pends upon  the  texture  and  structure  of  the  soil,  and  the  location 
of  any  particular  body  in  the  area.  Lands  immediately  adjacent  to 
either  the  channels  of  New  or  Alamo  Eivers,  or  the  tributary  washes, 
have  available  outlets  to  which  drainage  water  may  be  carried.  As 
the  distance  from  these  natural  drainage  outlets  increases,  artificial 
drainage  outlets  must  be  constructed.  As  these  drainage  canals  must 
be  deep  and  often  miles  in  length,  it  is  obviously  impossible  for  the 
individual  land  owner  to  construct  such  a  system,  and  the  work  can 
only  be  carried  out  through  the  concerted  action  of  groups  of  indi- 
viduals. Drainage  operations  may  be  financed  and  carried  out  by 
irrigation  districts  or  drainage  districts  may  be  organized,  under 
certain  State  laws,  whereby  the  land  owners  in  any  locality  may  or- 
ganize, tax  their  lands  or  sell  bonds  to  procure  funds  for  the  carry- 
ing out  of  drainage  works,  and  levy  taxes  for  the  maintenance  of 
such  a  system.  In  this  way  it  is  possible  for  large  areas  to  be  pro- 
vided with  a  thorough  means  of  draining  the  subsoil,  and  thus  effect 
the  removal  of  an}'  excessive  amounts  of  irrigation  water  and  any 
alkali  that  may  be  present. 


SOIL.  SURVEY  OF   THE  EL  CENTRO   AREA,   CALIFORNIA.  57 

SUMMARY. 

The  El  Centro  area  covers  540  square  miles,  or  322,560  acres.  It 
is  located  in  the  extreme  southern  part  of  the  Colorado  Desert, 
in  southeastern  California,  and  is  largely  below  sea  level.  The 
southern  boundary  of  the  area  is  the  International  Boundary  be- 
tween the  United  States  and  the  Mexican  State  of  Lower  Cali- 
fornia. The  area  includes  a  part  of  the  sloping  and  slightly  rolling 
area  of  the  desert,  above  an  old  beach  line,  but  consists  mainly  of  a 
more  level  uniform  surface  area  below  the  beach  line.  The  latter 
marks  the  shore  line  of  the  last  body  of  water  that  occupied  this  de- 
pression and  lies  but  slightly  above  the  sea  level  contour. 

The  higher  desert  sections  are  drained  by  a  number  of  charac- 
teristic shallow  drainage  ways  that  carry  water  only  at  long  inter- 
vals. The  discharge  of  none  of  these  streams  reaches  the  lower  part 
of  the  depression,  but  is  absorbed  by  the  sandy  desert  soils  above  the 
beach  line.  New  and  Alamo  Rivers  occupy  two  deep  gorges  in  the 
central  part  of  the  area,  and  afford  a  means  of  disposing  of  the  waste 
irrigation  waters.  Prior  to  the  recent  flood  from  the  Colorado 
River,  these  gorges  were  but  little  more  than  shallow  arroyos,  but 
they  are  now  from  50  to  100  feet  or  more  in  depth,  with  an  average 
width  of  about  1,000  feet.  They  discharge  into  the  lowest  part  of 
the  depression  now  occupied  by  the  Salton  Sea. 

El  Centro  and  Calexico  are  the  two  principal  towns  of  the  area. 
The  former,  which  is  the  county  seat  of  Imperial  County,  is  located 
near  the  center  of  the  area.  The  latter  is  located  on  the  Mexican 
Boundary,  about  14  miles  southeast  of  El  Centro.  Other  towns  in 
the  area  are  Imperial,  Holtville,  Heber,  Seele}',  and  Dixieland. 

Railway  transportation  is  afforded  mainly  by  a  branch  of  the 
Southern  Pacific  Railroad  which  extends  through  the  central  part 
of  the  area.  This  branch  connects  with  the  Los  Angeles  and  New 
Orleans  main  line  of  that  system  at  Niland.  about  35  miles  north  of 
El  Centro. 

The  climate  is  arid,  the  annual  rainfall  at  Calexico  for  a  number 
of  years  being  about  3  inches.  The  precipitation  occurs  during  the 
winter  months,  and  usually  comes  in  a  few  storms  of  moderate  to 
heavy  precipitation.  Slight  frosts  occur  during  the  winter  months, 
but  many  of  the  vegetable  and  small-fruit  crops  continue  to  grow 
throughout  the  year,  and  cotton  often  volunteers  from  one  season 
to  another.  The  summer  temperatures  are  high,  the  thermometer 
usually  reaching  100  degrees  or  more  during  every  month  of  the 
year  from  April  to  October.  Temperatures  of  116°  F.  and  117°  F. 
have  been  recorded  at  Calexico.  High  wind  movement  is  not  uncom- 
mon during  the  winter  and  spring  months. 


58  111  l.l'   OPERATIONS   OF   THE   BUREAU   OF   SOILS,   1&18. 

Prior  to  L900  there  were  qo  permanent  settlers  within  this  are*a, 
and  there  was  do  land  under  cultivation.  "Water  was  first  available 
for  some  of  the  land  north  Of  the  Mexican  boundary  in  1902  and  in 
1909  there  were  about  190,000  acres  of  land  under  cultivation,  and  a 
total  of  L,007  miles  of  main  and  lateral  canals.  The  leading  crops 
of  the  El  Centro  area  are  alfalfa,  cotton,  milo  maize,  and  barley. 
Specialized  crops,  such  as  muskmelons,  lettuce,  asparagus,  and  to- 
matoes, occupy  but  a  small  acreage ;  but,  as  they  are  intensely  culti- 
vated and  are  the  first  of  the  season  to  reach  the  larger  market  cen- 
ters, they  are  an  important  feature  of  the  agriculture.  Dairying  is 
one  of  the  important  industries,  and  the  winter  feeding  of  cattle 
and  sheep  for  market  is  growing  in  importance  each  year. 

A  large  acreage  of  the  farmed  land  within  the  area  carries  two 
crops  each  year.  The  truck  crops  may  be  succeeded  by  either  grain 
or  milo,  and  milo  or  grain  are  either  reseedecl  or  replaced  by  other 
early  maturing  crops. 

Below  the  beach  line  practically  all  of  the  material  of  the  soils  is 
derived  from  the  masses  of  sediments  transported  and  deposited  by 
the  Colorado  River  during  the  time  it  flowed  into  this  depression. 
The  heavier  types  of  these  soils  are  prevailingly  purplish  or  choco- 
late brown  to  brown  in  color,  very  compact,  and  sharply  stratified. 
The  lighter  textured  soils  are  of  a  similar  color  or  slightly  lighter 
brown,  but  since  their  deposition  have  been  subjected  to  redistribu- 
tion by  the  action  of  the  winds  and  have  a  rolling,  hummocky,  or 
duny  surface.  Above  the  old  beach  line  the  soils  are  prevailingly 
light  grayish  brown  to  light  gray  or  reddish  and  of  sandy  and 
gravelly  textures  to  indefinite  depths.  The  surface  is  often  quite 
uniform  in  topography,  but  is  also  frequently  eroded  or  rolling  and 
broken  by  the  occurrence  of  areas  of  Dunesand.  Seven  series  of 
soils,  including  21  types,  have  been  recognized  in  the  survey  of  this 
area,  as  well  as  3  classes  or  types  of  miscellaneous  materials. 

Irrigation  is  absolutely  necessary  for  the  growth  of  cultivated 
crops.  The  water  is  obtained  through  the  diversion  of  a  part  of  the 
flow  of  the  Colorado  River  at  a  point  a  short  distance  below  Yuma, 
Ariz.  Water  is  sold  to  the  farmers  at  50  cents  per  acre- foot  for 
each  24  hours  that  it  is  used.  To  this  cost  of  irrigation  is  added 
assessments  that  are  levied  for  the  maintenance  and  operation  of  the 
canal  systems.  About  75  per  cent  of  the  annual  water  delivery  is 
made  from  April  to  September,  inclusive. 

Alkali  is  quite  generally  present  in  the  soils  below  the  old  beach 
line,  excepting  where  they  have  been  formed  largely  by  the  action 
of  the  winds.  Above  the  beach  line  the  larger  part  of  the  soils  are 
entirley  free  from  alkali.  In  certain  rather  well  defined  areas  the 
amount  of  alkali  in  the  soil  is  so  large  that  the  attempts  at  crop 


SOIL   SURVEY    OF    THE   EL   OENTRO   AREA,    CALIFORNIA.  59 

production  have  seldom  been  profitable,  and  parts  of  such  areas 
are  not  now  under  cultivation.  Aside  from  these  bodies  the  aver- 
age amount  of  alkali  to  the  depth  of  6  feet  ranges  from  less  than 
0.2  per  cent  to  1  per  cent  of  the  air-dry  soil,  but  in  large  parts  of 
the  survey  the  salts  are  concentrated  in  the  subsoil  and  do  not  pre- 
vent successful  growing  of  crops.  Except  where  the  normal  distri- 
bution of  the  salts  has  been  affected  through  seepage  waters  there 
has  been  no  recent  concentration  of  the  alkali  and  there  is  little 
danger  of  further  accumulations  so  long  as  the  waste  and  seepage 
waters  do  not  accumulate  in  excessive  amounts.  When  such  con- 
ditions arise  a  very  complete  system  of  artificial  drainage  will  be 
imperative. 

o 


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